Ok we need to edit that list a little bit. Also, have you thought about needing a new XP or Vista license? I don't see that in your list.
1)7200.10 drive are old tech, get the 7200.11 or ES.2 drive. I've never seen a 250GB 7200.11 drive but I actually have the ES.2 drive and the 7200.10 250GB drives. the ES.2 drive IS SOOOOO MUCH FASTER:
http://www.newegg.com/Product/Product.aspx?Item=N82E16822148309
2)Roswill sucks at making PSU's, not to be negative, but they SUCK. Corsair makes a great PSU and are decently priced. Buy.com has then cheap with free shipping. The 520W is plenty for any 1 Graphics card setup.
http://www.buy.com/prod/corsair-520w-sli-certified-modular-atx-power-supply/q/loc/101/203270716.html
3)Zalman Coolers are Big and costly, save yourself a few bucks and get the AC 7 Pro. It's a GREAT cooler, I've owned on. Unless you are doing HIGH OC's on air you won't need anything more.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835186134
4)Dump the Quad core. If you are gaming or anything other than number crunching, you won't need a quad core. A faster dual core will toast a quad in 90% of apps. The only reason you would need it is video encoding and other things similar. The only people who need a quad core are the people who know for a fact that it would suit them better. Besides the e8400 is a MUCH better overclocker, and $20 cheaper.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115037
5)Not a suggestion but if you decide to keep the q6600, for some odd reason, dump the pc8500 memory for pc6400 (ddr2 800). You won't get a bus clock higher than 400MHZ on the Q6600 so there is no need for faster memory. There really isn't a benefit.
NOTES:
* Great video card selection, I have the XFX and like it alot. If it kept me warm at night I'd love it.
* Good mobo. Gigabyte and Asus are my choice brands. Although I lean toward Asus more for a little extra performance, but the cost is a little higher usually
* If you need the cost to come down we can easily trim it up a little. But that would be a solid build with the suggested changes.