So roughly 1878 USD / 1992 CAD / 1343 EUR / 1175 GBP
That's a big budget. Better get some questions out of the way.
Would you rather tone the system down and not spend all of it, or spend all of it and build a really amazing system?
Do you need a monitor, mouse, or keyboard? (for gaming you'll want good ones)
What do you want the case to look like? Can you post a few that you like the looks of?
Also, do you any accessories for the case? Maybe a fan controller or a remote?
Any other specific requirements?
edit: some more-
How much RAM do you want? At this price range you're probably going to want a Core i7 rig, which supports triple channel memory. Your logical choices are 3, 6, and 12 GB, though windows 7 home supports up to 16, and most motherboards can handle 24. You need win7 pro for that though.
I'd suggest 6, which would be 160-170 USD. Double it for 12GB.
What version of windows 7 do you want? There are retail and OEM versions of Home Premium, Pro, and Ultimate. OEM means that it's locked to the motherboard that it's first installed on, so you can't change your motherboard without buying windows again. Retail is more expensive but means that you can take it off of one computer/motherboard and move it to another.
Prices:
Home Premium OEM------$105 USD
Pro OEM---------------- $140 USD
Ultimate OEM------------$180 USD
Home Premium Retail-----$185 USD
Pro Retail----------------$275 USD
Ultimate Retail-----------$292 USD
This explains the different versions.
http://cdn2.windows7news.com/wp-content/uploads/2009/04/windows_7_features.jpg
Ignore Starter, Home Basic, and Enterprise...they're not available publicly.