Right now, I'm rocking a Phenom II X3 740BE that unlocked stably to a X4. It handles all of my apps and games without difficulty. It is on an ASRock 870iCafe mobo though, which is solid but lacks features, notably USB3.0 and more than one PCIE x16 slot.
Looking at the Best Gaming CPU charts, clearly there are many better CPUs than mine, but unlike the case with my past GPUs (7600GT, 7900GS, HD3850, HD4850, HD5770), I don't see an inevitable progression to something stronger being REQUIRED, at least not until there are huge AI advances in the mostly RPG titles I play. Still, I am definitely going to replace my mobo.
Sandy Bridge is expensive, as nice as it would be. I'm not sure I need it, at least not now. So, my plan is:
1. Wait for AM3+ mobos to come out (plus another couple weeks in case there are issues), then buy a high-end model (e.g. 990GX or FX with at least two PCIE x16 slots).
2. Use my current CPU on the new board, until / unless a CPU upgrade becomes helpful. Assuming Bulldozer is no worse than current Phenom II, I can still get a notably better CPU even if it isn't as nice as SB (which, for all we know, it actually could be).
If I do upgrade my CPU, I won't really have saved a lot of money, although I'll be able to sell the existing board and CPU. If I don't though, I will have spent maybe $175-$200 rather than $400+ on Sandy Bridge.
The viability of this plan is based on either or both of:
1. The performance level of Sandy Bridge will not be a requirement for good results from games for at least a few years, and/or
2. The performance of Bulldozer will be similar enough to Sandy Bridge that when CPU upgrade time does come, buying a quality AM3+ mobo will not turn out to have been a waste.
It really depends on how AMD does with Bulldozer's performance for the price.
Also, Sandy Bridge isn't as expensive as you make it out to be. Though it will run you ~$350 for the CPU/Mobo, the performance is incredible. The unlocked i5s outpace even the 6-core i7-900s, and they're the same cost as the previous generation i5s. Given AMD's record, I doubt they will be able to reach that kind of performance with AM3+.
Sandy Bridge won't cost $400+. When they had the boards listed, the best value board (ASRock P67 Extreme4) was $150-, and the i5-2500K is $225. That's a total of $375. And while the performance isn't necessarily required for gaming, now that that much power is out in the market, I'm sure games will scale up to met it much faster than anyone expects. Either that or you can sit on the same build for many, many years with minor upgrades.
I also doubt that Bulldozer will get similar performance to Sandy Bridge. I mean, AMD's been having trouble keeping up with Intel even before Intel dropped CPUs with 20-40% more power than the previous generation. Given that the old Core i CPUs already had a good 10-20% on AMD's "comparable" units, I highly doubt Bulldozer will have a 50%+ performance increase over their previous generation. After all, the jump from the old i5/i7 was phenominal. The kind of performance increase AMD would need is nearly impossible.
I'd personally wait for Bulldozer to actually be released before doing anything. I wouldn't spring for any AM3+ board until I knew the supported CPUs were worth it.
At an enthusiast level, that makes a lot of sense. From a marketing standpoint though, I'm not sure how quick developers will be to produce games that won't run "well" on a $600-$800 machine. Still, the games that interest me are the sort where CPU-hungry processes like AI could make a lot of difference. But then, if those are well-threaded, a current X6 might become relevant...but...and...
Well, nothing can happen anyway until the AM3+ boards are out. If that doesn't happen until Bulldozer is ready too, hopefully I'll get to see some benchmarks. I'd hate to rush to SB only to find that BD is "good enough" (I can't see it not being better than Phenom II) and/or cheaper.
its not a bad plan, older cpu's seem to do ok even in up to date games, I am currently using an old e6750 core 2 and it runs all the games I have thrown at it fine as long as I stay up to date on my gpu and thats running the cpu at stock, though I am now finally upgrading to a phenom II 955 BE, hpoe I can get 4+ years outa it like I did the intel