I have been eyeballing the rockford fosgate punch PBR mini amps. The 300 watt X 4 channel measures;

Dimensions (HxWxL): 1.53" x 4.25" x 6.75"
3.88cm x 10.79cm x 17.14cm

PUNCH Amplifiers - PBR300X4 - Rockford Fosgate®

It uses high level speaker wire inputs and has built in low pass and high pass X-overs. not bad for mid 200's.