IMO go for a gaming desktop, you could get build an amazing one for $700 at Newegg.com.
Gaming laptop? Can't really help you there. Depends on what you want to run in the long run since a good gaming laptop can run you up to $1200. If you just want to play SC2 then I suppose $700 would be enough. But honestly don't make that mistake, I made it a while ago with my old laptop. You get it just to play one or two somewhat recent games, maybe a year or so old, then down the line you'll curse it for it being unable to run newer high end games you want to play.