We talking £ or $? lol
Either way for 1500 you can make a pretty top notch system, if you plan on self building. (if you are a UK resident i can recommend a superb site)
I personally hate oem systems like dell and advent etc etc, 99% of the time everything in the bios is locked down so you cant overclock anything.
Once i get my new cooler my processor will be going to 3Ghz-3.2Ghz from the 2.6Ghz it is now (stock is 2.33Ghz lol).
Saving at the moment to upgrade my X1900XT 256Mb to a HD6970 2Gb. (ATI fanboy since my PII 300Mhz @400Mhz w/ ATI RAGE128 32Mb lmao)
As far as specs go you'd definately wanna go the i7-2600k route for your processor, will be top of the range for a while yet.
DDR3 is super cheap at the moment as well.
Well anyway closer to the time I can actually do some pricing for you etc, if you'd like, sorry by the way, building new pc's get me excited!
Edit: Haha just noticed the $$ in your post, well i dont know as many US based websites selling PC's/components, but will look into it closer to the time.