Upgrade to 2500k NOW?

Your question really comes down to how much money you have to spend on your upgrade. Switching from an FX 6100 Bulldozer to an i5 2500K Sandy Bridge would be an upgrade and give you better performance, however Zen should be a large step above an i5 2500K. For a little background knowledge lets take a look at Intel's lineup and then take a look at what Zen is projected to be.

First of all Intel i5 Sandy Bridge (the i5 2500K) is first generation iCore so processors like the new i5 6500(K), which is Intel Skylake (fifth generation iCore) will be a much greater upgrade (and also cost much more). Really at this time I would suggest if you going to upgrade you should be looking at no less than an upgrade to Intel Haswell (something like the i5 4690K) as a lot of newer games are already calling for a minimum processor greater than the i5 2500K. Realistically an i5 4690K will keep you gaming though the lifespan of the current console generation (PS4 and Xbox One). I'm using gaming as a standard here as most people looking to upgrade (especially to Intel) are upgrading for gaming purposes.

Now a look at what Zen is projected to be. Zen is supposed to have a 40% IPC gain, however it is important to note that the 40% IPC gain is over Excavator, not Piledriver (which already has a nice IPC gain over the Bulldozer arch your currently running). Taking all that into account comparing Zen to AMDs current flagship FX 8370, Zen should have around a 60% IPC gain over the FX 8370. That will place Zen around the same IPC as Intel's Haswell arch. That is a very big jump in performance for AMD, however processors like Broadwell, Skylake, and the upcomming Kabby Lake will all have better IPC then Zen. Zen however does have an "ace in the hole" as AMD has leaked that Zen will be released first in the enthusiast market as Zen FX and will feature an 8 core 16 thread processor. To compare that against Intel's offerings i5 processors are 4 core 4 thread, standard i7s are 4 core 8 theads and the very top tier i7s are 8 core 16 thread (and usually have $1000 price tags). AMD has not released what Zen will be clocked at, however if Zen is at the same IPC as Haswell in single core performance Zen will be outperformed by Skylake, Bradwell, and Kabby Lake. However the "rub" is in multi-threaded applications (which the vast majority of newer applications and games are) Zen with 8 cores and 16 threads should outperform all but the most expensive i7 processors (i7 8 core 16 thread processors) through Skylake. Zen should be able to outperform i5 and 4 core 8 thread i7 Skylake processors (in multi-threaded applications and games) and would be a very good upgrade over a processor like the FX 6100. Zen will of course require the all new AM4 platform (motherboard) and will require DDR4 RAM and we don't yet know where AMD will be pricing Zen.

With all that information, my personal recommendation would be to hold off now until October (when AMD has stated Zen should be available) and is just a few months away at this point and see what Zen's release does to the industry. If Zen releases at Haswell IPC performance and is running the 8 cores and 16 threads that AMD has leaked it should give even i7 Intel Skylake processors a big challenge in the high end CPU marketplace and could drive down prices across the board. Historically Intel doesn't like to lower the price of their CPU line, however if they have real competition again it could force them to do so. At that point you could decide if an upgrade to Zen or something like the i5 4690K would be a better fit for you. If Zen forces competition and lowering prices you might even be able to pick up something like a i5 4690K at half the cost that it would cost you now, or is Zen is priced to really compete it may be the best upgrade depending on your budget.

Your question really comes down to how much money you have to spend on your upgrade. Switching from an FX 6100 Bulldozer to an i5 2500K Sandy Bridge would be an upgrade and give you better performance, however Zen should be a large step above an i5 2500K. For a little background knowledge lets take a look at Intel's lineup and then take a look at what Zen is projected to be.

First of all Intel i5 Sandy Bridge (the i5 2500K) is first generation iCore so processors like the new i5 6500(K), which is Intel Skylake (fifth generation iCore) will be a much greater upgrade (and also cost much more). Really at this time I would suggest if you going to upgrade you should be looking at no less than an upgrade to Intel Haswell (something like the i5 4690K) as a lot of newer games are already calling for a minimum processor greater than the i5 2500K. Realistically an i5 4690K will keep you gaming though the lifespan of the current console generation (PS4 and Xbox One). I'm using gaming as a standard here as most people looking to upgrade (especially to Intel) are upgrading for gaming purposes.

Now a look at what Zen is projected to be. Zen is supposed to have a 40% IPC gain, however it is important to note that the 40% IPC gain is over Excavator, not Piledriver (which already has a nice IPC gain over the Bulldozer arch your currently running). Taking all that into account comparing Zen to AMDs current flagship FX 8370, Zen should have around a 60% IPC gain over the FX 8370. That will place Zen around the same IPC as Intel's Haswell arch. That is a very big jump in performance for AMD, however processors like Broadwell, Skylake, and the upcomming Kabby Lake will all have better IPC then Zen. Zen however does have an "ace in the hole" as AMD has leaked that Zen will be released first in the enthusiast market as Zen FX and will feature an 8 core 16 thread processor. To compare that against Intel's offerings i5 processors are 4 core 4 thread, standard i7s are 4 core 8 theads and the very top tier i7s are 8 core 16 thread (and usually have $1000 price tags). AMD has not released what Zen will be clocked at, however if Zen is at the same IPC as Haswell in single core performance Zen will be outperformed by Skylake, Bradwell, and Kabby Lake. However the "rub" is in multi-threaded applications (which the vast majority of newer applications and games are) Zen with 8 cores and 16 threads should outperform all but the most expensive i7 processors (i7 8 core 16 thread processors) through Skylake. Zen should be able to outperform i5 and 4 core 8 thread i7 Skylake processors (in multi-threaded applications and games) and would be a very good upgrade over a processor like the FX 6100. Zen will of course require the all new AM4 platform (motherboard) and will require DDR4 RAM and we don't yet know where AMD will be pricing Zen.

With all that information, my personal recommendation would be to hold off now until October (when AMD has stated Zen should be available) and is just a few months away at this point and see what Zen's release does to the industry. If Zen releases at Haswell IPC performance and is running the 8 cores and 16 threads that AMD has leaked it should give even i7 Intel Skylake processors a big challenge in the high end CPU marketplace and could drive down prices across the board. Historically Intel doesn't like to lower the price of their CPU line, however if they have real competition again it could force them to do so. At that point you could decide if an upgrade to Zen or something like the i5 4690K would be a better fit for you. If Zen forces competition and lowering prices you might even be able to pick up something like a i5 4690K at half the cost that it would cost you now, or is Zen is priced to really compete it may be the best upgrade depending on your budget.

And then you can go back and look at the hype of all the older AMD releases that were a flop.
Even if they get the 40% increase it still would only put them at about the single core performance of the older 2500K.

And then you can go back and look at the hype of all the older AMD releases that were a flop.
Even if they get the 40% increase it still would only put them at about the single core performance of the older 2500K.

And you may want to check your math, or lack there of. A 40% IPC gain over Excavator (roughly 60% IPC gain over Piledriver) would place Zen at Haswell IPC not Sandy Bridge IPC. Single core performance of Zen should be equal to Haswell (ie 4690K) not Sandy Bridge (i5 2500K). Saying that the i5 2500K has more than 60% IPC over Piledriver is horrible misinformation.

All speculation I can't think of a single time AMD has delivered and so no reason to believe them this time.
For the price he can get the board and 2500K for he would be foolish not to get it 135 bucks compared to a full rebuild.

So just to make sure we're on the same page: The 135$ for this combo is also about the highest limit of money I am willing to spend, now and in three/four months. And I'm not sure, if Intel will drop their prices this aggressively to 65$ for a newer Core i5-K and the same for a Z-Mainboard...

Thank you so much for your time and help. I think I'm gonna get the 2500k and the ASRock Mainboard und sell my FX and MSI Mainboard.

Very good choice that processor should last you 2 / 3 more year at the least. Games are not going to suddenly make that processor a bad choice their no game out the my 2500K PC can't run and I can not see that changing anytime soon.
That processor is still as good as ANY AMD processor made for gaming.
http://www.tomshardware.com/reviews/cpu-hierarchy,4312.html
Take a game like Overwatch A 2500K just at stock speed beats ANY AMD processor out.
http://www.techspot.com/review/1180-overwatch-benchmarks/page5.html
The list goes on and on.
http://www.techspot.com/reviews/graphics-cards/gaming-benchmarks/

2-3 years is an extreme stretch. Telling people that first generation iCore is going to be just fine gaming anything for the next 3 years is going to lead to a lot of buyers remorse. Like you right now I can run any game going on all Ultra settings 1080p 60+FPS, but give games another year, year and a half at most and that won't be the case. Realistically another year to year and a half and it will be time to upgrade. Hopefully by that time Zen will be a player in the high end CPU market and will drive price and competition and by the time we all have to upgrade it will be to a much better platform at a better price than we currently have.

and 1.28V