not that my rig is perfect for you or anything but I was in the same situation as you about a month ago when i bought this.
it was around $1250 US or £990 with OS, keyboard, mouse and monitor and around 1050 or £830 without OS...etc
the graphics card could be better but i can still max out the graphics settings on most games right now. depends if you have the cash to up it from 7600GT to 7900GT. i only got the 7600GT cuz it was a better "bang for the buck"
you could probably go with an E6300 instead of E6400 since they're nearly identical except one is around £40 more for just a 5-10% increased speed.
if you can get 2GB of cheap DDR2-800 ram (mine is expensive and nice ram that was around £120 for 1GB and you should be able to get a 2gb (1gb x 2 sticks) kit for around £160-170)
i highly recommend the PSU
basically...i think that a rig similar to mine would be really good for what you'd be able to get.
my suggestion is to look at what i've got and then pick and choose parts to replace what i've got. That'd be easiest for you.
Antec NeoPower 650W
Intel Core 2 Duo E8400 (w/ Arctic Freezer 7)
4GB DDR2-1000 G.Skill
Sapphire x1950 Pro 512mb (w/ V700)
250GB, 500GB and 1.5TB Seagate Barracudas (2.25TB total)
Fatal1ty XtremeGamer sound card *** generic TV tuner
Xclio 3060 case *** HannsG 22" monitor
XP Pro / Ubuntu 7.10 *** Razer Copperhead and Tarantula