Starcraft II Requirements
I say a 9800 GT
should put you in high settings. But if i were you, i'd aim for something higher that's only a couple $$ more =P like a GTS 250
. A little more power than you need, but just to be safe lol.
Now keep in mind these cards won't be supporting DX11 - but i'm assuming you don't want that (much less need it)?
And everything else is fine, no worries there =)