Im currently running a Dual Core Pentium 3 gighz. I'm looking to upgrade to a either an i5-2500k or an i5-2550k. Is there much of a performance difference in either i5's? I'm pretty much a novice in when it comes to cpu's and gpu's. Also, my gpu is an ATI 5750 is this a descent card to run games like Rift or Guild Wars 2 or will I need to upgrade that as well?
I think the difference between the 2550k and the 2500k is the 2550k doesn't have the integrated graphics onboard. In theory the 2550k is supposed to give you better overclocking, but this point is moot since both of them overclock massively.
The 2550K has a 100MHz stock advantage (including turbo boost) and lacks IGP.
As for overclocking, I don't think there is any advantage, as they both come from the same production line. That 100MHz advantage could be due to IGP missing power consumption.