I'd suggest a Caviar Black, even if the increased performance is not taken advantage of, the additional cost is only about $5. I also always lean toward Corsair for PSU, though there's nothing wrong with OCZ.
You're going nVidia with AMD, which again there's nothing wrong with that, it's just not the norm - most people pair AMD with ATI or Intel with nVidia. If your budget allows it, you'll have more upgrade-ability with an Intel i7 and a GTX 260 core 216 video card is a pretty nice upgrade. These things all add a fair bit of cost, but with performance increases that make it worthwhile if not unaffordable.
If not, I'd consider two ATI cards in Crossfire over the GTS 250 http://www.newegg.com/Product/Product.aspx?Item=N82E168... is a good example since two will be the same cost as your one nvidia card, however you may need to select a different mobo, it doesn't appear this one is Crossfire compatible