Kar'fi & Gurumba are the only Klingon ships I'd buy based on performance alone from the C-store. Maybe a Bortasqu' Tactical.

I'd pick up a Vandal Destroyer specifically for the Plasmonic Leech console. It's also a solid ship for leveling around that range.

The Fleet Scourge, Fleet Tor'kaht, & Fleet Hos'sus are the only ships I'd buy from the Fleet.