Here's a few changes that could be made to fit in your budget.
Antec Three Hundred 53.99
AMD Phenom II X4 955 215.98
Gigabyte 790XT-UD4P 142.40
Corsair TX750W 111.99 Leaves much more room for upgrade and cheaper after MIR
G.Skill DDR3-1333 9-9-9-24 2x2gb 89.99
Powercolor HD4890 199.99 Gives a bit more power for a gaming rig and is nearly same price after MIR.
Total: 814.34
Shipped at my door for example with insurance: 903.09
MIR (which were not factored in any prices): 57$
Edit: If possible I'd try to get a bit bigger case for cable management... and an aftermarket cooler such as the Coolermaster Hyper 212+ so that you can overclock the CPU and get the most out of it.