Corsair, Antec, Seasonic, PC Power and Cooling, Silverstone, and Enermax all make great units. As for budget that more depends on what wattage/amps you need. The Corsair 400CX is a great little unit that is on sale for $29 after rebate this month from newegg.
Post your system so we can tell what you need.
That Corsair 400CX will work fine for that build. Hard to beat a quality unit for that price. It will NOT be quite enough if you plan to run Crossfire later though. If you plan on upgrading graphics to the HD 5850 level anytime soon go for the Antec unit delluser1 recommended. If you are going to stick with the GTS 250 the Corsair is fine.
Edit: I am an idiot...you obviously can not Crossfire Nvidia cards.......lol.
What resolution is your monitor and what games are you going to be playing? The best card in that price range ( a bit more ) is the HD 5770. That GTS 250 is the same card as my 9800GTX+ and while it is still a good card at lower resolutions it is starting to show its age. The HD 5xxx series are newer, use less power, overclock quite well and have the advantage of DX11 support if you are using Windows 7 as well.
You are going to want an HD 5770 or even better an HD 5850 if you can afford it. Crysis is still one of the most demanding games out there. At 1920 resolution a 5770 is decent and a 5850 can play just about everything.