Quote: "the deafult computer today is a smepron 3000+, 512mb ram, ati x200, s-ata drives"
The X300 was bad enough... sodding aweful cards until you get into the reasonable price-range.
If you want a cheap PCI-E card with backbone, GeForce 7300 all the way. It doesn't touch the 7800 or 7900, but it can out-perform a 6600GT with ease. For £50 you can't really complain at that.
I'd say the standard computer currently is:
2.5GHz Pentium 4 / Athlon64 3000+
256MB SDRAM
On-Board Sound (usually C-Media or AC'97)
GeForce 5200/6600 / Radeon 9550/9800 Equivilant
Mouse & Keyboard
17" TFT Monitor
DVD-RW Drive
250GB ATA/133 or S-ATA 150
Those would be the most common stats I've seen.