Current hard drive prices are going to make this difficult.
First of all, I don't really like this build, as I think it makes too many compromises. I'd also think I'd rather do Intel for overall better performance, but the compromises I think would be worse. If you can get the budget increased to $600-$650, a much better system could be built. Anyway, here is a build that can play SW:TOR:
AMD Athlon II X3 455 Rana 3.3GHz Socket AM3 95W Triple-Core Desktop Processor ADX455WFGMBOX
Model #:ADX455WFGMBOX
Item #:N82E16819103911
$79.99 $79.99
I'd rather use an Intel i3, but the sacrifices in mobo quality would make the whole build a waste.
HITACHI HDS721050CLA362 (0F10381) 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
Model #:HDS721050CLA362
Item #:N82E16822145299
$89.99 $89.99
There's no great choice in drives now. There are some 160GB drives available for only $5 less, but I suspect that's a bit too low for the entire system.
G.SKILL NS 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model F3-10600CL9D-4GBNS
Model #:F3-10600CL9D-4GBNS
Item #:N82E16820231394
$20.99 $20.99
8GB is pretty common, but for a budget build, this will do. I have had only good results from G.Skill.
Antec EarthWatts Green EA-430D Green 430W Continuous power ATX12V v2.3 / EPS 12V 80 PLUS BRONZE Certified Active PFC Power ...
Model #:EA-430D Green
Item #:N82E16817371034
Mail in Rebate
$59.99 -$10.00 Instant $49.99
The 380W version is $5 less, but if you play the rebate game and win, this one works out to be cheaper. It also has free shipping. The Antec Earthwatts PSUs (especially the "D" models) are all solid and quiet.
PowerColor AX6770 1GBD5-H Radeon HD 6770 1GB 128-bit GDDR5 PCI Express 2.1 x16 HDCP Ready Video Card
Model #:AX6770 1GBD5-H
Item #:N82E16814131434
Mail in Rebate
$114.99 -$5.00 Instant $109.99
The MIR, again if you play that game and win, brings this one down to the price of a HD6670. It would be nice to have a stronger card here, but on the stated budget, I think this is probably about the best you'll do without making something else too much worse.
Rosewill Blackbone Black Steel / Plastic ATX Mid Tower Computer Case
Model #:Blackbone
Item #:N82E16811147023
$49.99 -$5.00 Instant $44.99
I have built in this case. Like all the low-mid range Rosewill cases I've used, it has plenty of room, minimal sharp edges, and the fans are quiet but effective. In my experience, it also won't have the trivial but always present quality issues you'll likely find in Coolermaster's cheap cases. It has free shipping, which can add $10-$15 to the price of many cases.
ASRock M3A770DE AM3 AMD 770 ATX AMD Motherboard
Model #:M3A770DE
Item #:N82E16813157176
$59.99 $59.99
Best described as an old standby, this mobo is getting a little dated, but it is cheap and solid. It has performed well in some of the cheap SBM builds, and I've used it a couple times myself. Bulldozer was such a fail that not being socket AM3+ really doesn't matter.
Sony Optiarc CD/DVD Burner Black SATA Model AD-7261S-0B LightScribe Support - OEM
Model #:AD-7261S-0B
Item #:N82E16827118040
$19.99 $19.99
One optical drive is much like another, although this one has Lightscribe.
Subtotal: $475.92
By the time you add shipping, you may push on your budget a little, but then hopefully you'll get at least one of the MIRs back.
It isn't a great build, but I think it would be hard to do better on your budget.