best amp for BASS

My system is in a relatively large room 25x40 with 25ft.ceiling..It is a 5.1 system with meridian 861 and 800.German physics speakers.The Main speakers are Loreley large speakers each having four 12in.woofers.These are bi amped with Xover at 200Hz,with 6db slopes.At present the amps are YBA Passion 1000 mono blocks for the highes(fantastic) and bryston 14bsst for bass.The bass is OK but definitly not great.I would like to augment the bass amp.any ideas?