If it's Imperial Fists I'd definitely aim at a Sternhammer Strike Force. It can be done for 750 points (see below) & that would give you 250 more for upgrades/anti-air, extra Devastator "wounds"/transport or whatever else you wanted
STERNHAMMER STRIKE FORCE
Core (Battle Demi Company)
Chaplain (90 points)
Tacs (5man) Meltagun, Combi Melta + Rhino, dozer blades
Tacs (5man) Meltagun, Combi Melta + Rhino, dozer blades
Tacs (5man) Meltagun, Combi Melta + Rhino, dozer blades
(390 points)
Attack bike (HBolter) (40 points)
Devastators (5man) + MLx4 (130 points)
Auxillary choice:
Thunderfire Cannon (100 points)
750 points total! And you still have 250 left!!!