I won't strech myself in completely alternative configurations because I don't play SC2. I'll just give you a warning, that combo has a very nice and multiplier unlocked 80W 550BE X2 CPU, designed for overclock and that might even unlock to 3 ou 4 cores if bios permits. But don't even try to mess with, that board only accepts 95W CPUs, which is a very bad sign.
The next slightly more expensive combo at $263 with a gigabyte board
here seems a better deal. That GA-M68MT-S2 supports 125W Cpus and core unlocking, so you might try your luck to turn it into a X3 (if possible on that bios when a disabled core is damaged) or four core given some luck (while putting you at the MBs TDP limit), or simply boost it a bit for a couple multipliers which shouldn't even require a vcore adjustment (unlocking and OC at the same time is a big NO given the rest) as you have a small 45W margin to play. A 1090T X6 is even in the supported CPU list, not that I'd trust it to abuse. Btw, you might have to change that CPU cooler before any adventure, I'd even be afraid to run it stock as a little search shows it rated for only 65W, but current manufacturer specs also list phenom X4 II so I don't know what to think about something that looks even worse than the stock amd cooler.
That combo also brings a 1TB drive instead of 500GB and slight more powerful 450W PSU (from 400W, albeit equally dodgy), as these configurations have onboard GPUs and weren't intended to add a dedicated card. So don't slap something hungry on the GPU side, that 520GT shouldn't pose a problem as they seem to draw ~30W maximum in some reviews. A GT430 is about 70% faster due to double the amount of shaders and texture units, you can find them equally for about $40 in NCIX after rebate, but power consumption will top at ~50W.
Btw, SC2 doesn't seem to scale much over 3 cores.
