SLKR is always a good first GL. Sith Empire is still a good team, but you might be pretty far off on that one looking at your roster. With some gearing, you could put a pretty good Empire team together. Core is Palp lead, with Vader and Thrawn. I generally throw in Royal Guard and Tarkin at this point since I keep my Imp Troopers separate. Imp Troopers is the other must have Dark Side team.
Really, as you work on the dark side GL's, it helps you build other teams.