Just an info about my system specs and what I've paid, maybe you can get a picture of where to save some money.
C2d 6550 boxed(as fast as the 6600) 150€
2x1gig of geil ram 100€
sapphire radeon hd2600xt 130€
nesteq 450W 70€
sharkoon rebel9 eco 35€
msi p35 neo2-fr 100€
That's a nice rig for 585€ (something around 400 pounds), I took the hdds and dvd burner out of my old computer.
My screen is an acer al2216wd, YES, it's a bloody tft and it was cheap, but its enough to play, do skins and watch tv on.
On a normal lfs installation I get at least 100 frames (at 60Hertz :-)), mostly around 180. I've got high res skins, tyres, tracks and the like, full graphics and still around 100 fps.
IMO you should buy stuff to USE, not to show off having good numbers standing in your sig. Don't ask for a new 911 when you can only afford some used Vauxhall ;-)
greetz
der butz