just fyi, games these days are all in the RAM and graphics card, the CPU makes very little difference until you want to go into photoshop or video editting.
i accedently discovered this myself and it was quite a revelation. i got myself a ATI HD3850 256mb, and 2GB DDR RAM. i wanted to get the phenom processor too but coudlnt afford it just yet, so i went out and got the cheapest socket AM2 cpu i could find, which happened to be the X2 3600, with a standard heatsink and fan.
plays crysis on high detail (DX9, i'm on XP), on 1680*1050 just fine, and most other games on highest settings.
the FSB of the CPU was 2/3 that of my RAM, so i overclocked my CPU from 2ghz to 3ghz (increased FSB and voltage, decreased multiplier) so my ram could operate at full capacity, and the it still runs at room temp and stable as anything (possibly thanks to my case's cooling though).
so i figured, i'll stick with this, i dont need a CPU upgrade just yet...
so, dont go spending £100 on a cpu + £50 cooling for a gaming rig when you can get just as good performance with a £35 near-obsolete (the shop doesnt sell 3600's any more) cpu + £10 for standard heatsink and fan, thats just my advice.
as for the GPU, my HD3850 is lovely, though i did have a problem of artifacts even though the GPU was running at very low temp, but the new cooler i got for it is rather awesome, the gpu ran even cooler and the artifacts disappeared 99% of the time, i recommend the cooler to anyone, (its also compatable with NV cards). i got the card when it was first released on the market, since then the standrard cooler has been improved aswell as the card itself.
i'm sticking with XP for now. apparently the arguement is that vista does perform better than XP as long as you have recent hardware, and my hardware is pretty new so i should in theory be getting vista. however, i have an XP disk, im perfectly happy with xp, so dont see why i should throw it away for vista. i heard vista really sucks when it comes to "nannying" the user, asking 50 million times if you're sure you really want to open the email attachment, and that really puts me off, as much as i hate linux, i think i'd rather switch to that than vista.
it is possible to crack DX10 for XP, its not even that hard, all you do is copy and paste a few DLL's. I've done it, and i noticed after i did it, DX10 enabled games gave me graphics settings that would only be enabled if i had DX10 installed, so it seems the crack worked, except when i pay the games i only see an increase in framerate, but not much else in terms of eye-candy..
so there, my 5 cents, glad to have been of help.
edit: forgot to include the link to my thread about the cooler.
http://forum.thegamecreators.com/?m=forum_view&t=124778&b=2