For the processor - you are spot on in the selection. Nearly as good performance as a $100 more i7, for gaming kicks the crap out of anything AMD currently has (unless you are the overclocking type where AMD overclocks better currently).
For the motherboard - Is there a particular reason for this selection? A feature it has that you need, brand loyalty, style? I wasnt even aware EVGA made motherboards, but in my experience, once you get above the jetways and foxconns to the real brands, most motherboards these days are created equal. You could score a biostar or even an ASUS with similar specs for about $50 less
For the video card - The GTS 250 is basically a 9800 - ie 2 generations old, and slower than ATIs previous generation. Unfortunately, the 4850s and 4870s arent on the shelves any more most places. If you can find on of them, it should be about the same price point. If you go with a cheaper motherboard, you could fit a Radeon 5770 into your budget. The 5700 series isnt going to knock your pants off (its actually the same speed as a 4870 really), but its faster than a GTS 250 for about $30 more, and gets you direct x 11 support, and better multi-monitor selection. Of course, if you want to save a bit, I have a couple 4870s in my computer that I want to upgrade to a 5870, and would sell one at a reasonable price
I'd rather run all 3 of my monitors off of one video card than two.
For Memory - $100 for 4 gigs of ddr3 from a name brand? Go for it.