The way I build computers is this
I put the 'fixed costs' I.E. Motherboard, case, PSU, HDD, ODD, Windows etc into one tally. These don't change no matter what you choose.
Then I put the performant items into another tally this is the CPU, Graphics card and quantity of memory as these can be varied as much as you want.
Then I try to find the best balance between price / performance by chopping and changing the CPU, GPU, and memory to find an appropriate balance.
However you also have an alternative:
http://www.newegg.com/Product/Product.aspx?Item=N82E16883227291
Something like that would be excellent for media and games and that 5770 is all you need for Starcraft 2.
It depends on how comfortable you are with building a system.
Tease.