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?