Yes at one time it was cheaper to build your own system, now there is so much competition that it dosnt cost any more to buy a built system if you look in the right places. I cant suggest any as i am in the UK. My PC runs Realfight 4.5 and Aerofly Deluxe with no problems and no stutter at all at 1680x1050 but i think it would run just as well on a lesser system as i dont seem to be pushing my system at all.

Q6600 @ Stock 2.4Ghz
4GB Ram 667Mhz
Nvidia 8800GTX 768mb
Vista 32 Bit (Not using all ram with this 32bit version but not upgraded to 64bit as some of my software will not run)

Cheers Lee.