Yeah, I've been looking into getting a tower. Don't need something that plays all games at max graphics. But better than a laptop will do fine. Was looking at geforce 400 cards and a few gigs ram. But the naming grades for CPU still eludes me.
i3 is weakest, i5 is midline, cheaper than i7 but with a good enough graphics card, runs games fine. i7 (or i9 and i7xx) are the highest grade, with the best speeds.
2600k is a great i7, quad core, good to OC, and handles most current games with ease (it will run Crysis 2 along with a GTX 590 on max settings with fraps also running).
Get yourself a GTX 560ti (or a pair in SLI) and you'd be fine.