mid/high end gaming computer

Since you aren't doing SLI and (IMO) DDR3 is much less performance for the price compared to DDR2, I would switch to a much cheaper P35 motherboard and DDR2 memory. That's $300 right there, almost enough to get a nice 24" monitor to go with that GTX280. Or, if you already have a monitor, think about another hard drive for Windows.

You could also probably get away with a PSU between 600 and 700 watts depending on the brand,

X38 is a Crossfire board. You are getting a Nvidia card.
Do you want to switch to AMD?
Or do you want to go the 790i route?

Please do not get a P35 mobo. Go for an X48 for best performance. It appears as if you are willing to pay top dollar for your parts, so here is what i recommend. Good choices for everything except mobo and cpu cooler.

Here are my recommendations:

Thermaltake Armor+ (it has a removable mobo tray)
http://www.newegg.com/Product/Prod [...] 6811133056

Gigabyte X48 mobo
http://www.newegg.com/Product/Prod [...] 6813128330

G Skill (2x2GB) at tight timings RAM
http://www.newegg.com/Product/Prod [...] 6820231167

CPU Cooler
http://www.newegg.com/Product/Prod [...] ndetta%2b2
or
http://www.newegg.com/Product/Prod [...] 6835887011

Thermal Grease Artic Cooling MX2
http://www.newegg.com/Product/Prod [...] oling%2bmx

DVD Burner (Samsung is much better and cheaper)
http://www.newegg.com/Product/Prod [...] 6827151154

PSU (modular Corsair and cheaper)
http://www.newegg.com/Product/Prod [...] 6817139007

HDD (Samsung Spinpoint [32 mb cache] and faster than Caviar and quieter)
http://www.newegg.com/Product/Prod [...] 6822152100

I personally have a Q9450 myself but its a pain to overclock. However, the Q9450 is a great cpu. You can easily OC it to 3.2 GHz amd have it run in 1:1 with your RAM at 1600 MHz speeds. However, anything more than 3.5 GHz will require days of work. Most people experience FSB limitations after ~460 FSB. I haven't been able to get past 450. Hope this helps and by the way I doubt you will experience any lag in games since you're gettin a GTX 280.

btw theres a combo deal on the q9450 with the psu i just posted its a $30 instant rebate

I think you're spending too much on the case, probably should look at a Xigmatek s1283 Cooler over the Freezer 7, and would be better served at less cost by two 9800GTX in SLI (but not on that motherboard).