MOBO - ASUS P7P55D-E Pro - $179.99 http://www.newegg.com/Product/Prod [...] -_-Product
Cheapest board that Fully implements usb3 and sata 6gbps, a bit expensive, but is a really nice board. Some other people my suggest getting cheaper less feature packed boards, completely up to you, choose your buget
GPU - Ati 5850 - $279.99 http://www.newegg.com/Product/Prod [...] -_-Product
the 5850 will be great at those resolutions for a long time, and if you decide to go a bit bigger on the next monitor, it will cover that too
CASE - CM Storm Scout - $89.99 http://www.newegg.com/Product/Prod [...] 6811119196
Nice portable case (i guess thats why you chose it)
if you want better airflow, go for a CM haff 922, they are similar prices
DON'T get that PSU. I would recommend going with the Corsair 750TX. This has plenty of headroom for future GPU upgrades, and a nice OC.
Stick with these brands for PSU, Antec, Corsair, SeaSonic, Silverstone, PC Power and Cooling, OCZ (on a budget)
There is probably a factory overclocked HD5850 that will cost more, though I would look for one that has better cooling in mind. Usually HIS and Sapphire offer better aftermarket coolers on their GPUs.