When I built my pc, I got an Intel Core Duo 4300 which is 1.8GHz stock and o/c'd it to 3GHz simply by upping the fsb speed. At the time, all of the 4300's would do it, but I'm not sure if it's still true. I believe the E6600's are good o/c's too.
Here you go!
http://www.tomshardware.com/2007/07/19/system_builder_marathon_day_3/
Note that they went with a $500 video card, I got an ATI x1950 for about $130. There really isn't a nice DX10 card right now in the midrange price.
Ok, so my recommendation is to put together something similar to the setup on Tom's, but get a cheaper video card and upgrade it in a year or so when DX10.1 is more mainstream and the cards are cheaper. I'd also look into getting a better processor, possibly the E6600 and o/c it. Search around the internet and there'll be plenty of articles similar to the one on Tom's, but with different hardware used.
Looking at the list that you put together, I have one really big problem with it. DO NOT skimp on the power supply. It's the number one system killer that everyone always overlooks.
P.S. I know all the console users always freak out about how much it costs to upgrade your pc. If you know what you're doing, set aside a couple hundred bucks a year and you'll pretty much always have a competitive pc. One year, upgrade the video card, next year add more ram, next year cpu/mobo. You get the idea. IMO, it's really fun because you're always anticipating what you'll do next!
