not sure how small of a footprint you looking for but maybe the SD500.4 fits your needs? does 124x4@4 ive ran one ond they are actually really nice...far from the power hogs they have for spl. mine put out good clean power. not the most SQ amp in the world but it did sound pretty **** good.
Thinking I'm going to stay with the infinity amps....small, powerful, sleek and I haven't seen any better ones good small enough to switch.......JL's new compact HD line is nice.....but highly priced....would luv a couple used ones lol
Ive got a BNIB SoundStream DTR4.500 for $100 shipped they mount vertically but also have mounting feet in the box to mount it horizontally like a normal amp if needed. Haven't posted it up yet but its sitting in the box right next to me...