for the money you have the i-5 2400 at micro center is 140.00 then pick up an 8g ram kit. you never need to add more ram and there cheap right now. if not just pick up one 4g dimm. the x68 chipset mb will be fine. it give you sats 6g ports if you want to use a fast ssd as a boot drive.
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157271
are not a bad mb for the price and have done well on toms hardware roundup. other brands are asus and gigbyte and msi. the trick is to google the model your looking at to see if there any bugs or high doe rate with that brand or model. it also good to look at the mb forums of the vendors to see if any board issue. with video cards right now is to get one at good price to performance. the 6870 if you can find them are a good card at a good price. on nvidia side right now is the 560 line of cards. when the 660 line comes out and the price drops people like toms will be giving them thumbs up for price and performance.
the only thing i add is dont be cheap on your power supply. to cheap and it can fail and take out your whole pc. look at the reviews online at other forums that put ps under load test. good power supply will not have a lot of ac ripple when loaded and the three main power legss should not drop a lot (stay within atx spec). a lot of cheap over seas power supply will say there 500 or 700w ps but there parts are made for less wattage and under full load go boom..hardcorps forum have had few ps that took out there test bench...