If Phenom II X4 costs "too" much then forget about playing Crysis on that machine.
Intel's i3 2100 costs almost the same and its a good gaming procesor, too. Anything below that cant run Crysis or GTA 4 properly. Core2Duo etc will just be the bottleneck for your PC.
Buy Win7 64bit and get atleast 4GB of RAM to even dream of running those games.
Try to find this motherboard. It's aroung 60-70$, it has high quality parts (all solid capacitors) and it's upgradeable to Bulldozers. The only, if you can say it bad thing, is that it doesn't have SATA III ports. But that's acceptable considering that HDDs don't get any perfomance increase from it!