Overkill Audio uses the 150A Reference for its $75,000 Encore system. They charge $8k extra for a four channel version of this amp. Not a bad endorsement at all. I think it has one of the fastest slew rates of any amplifier, if not the fastest.
If you're looking for a smoking deal on the Belles, you can get two separate 150A Ref in one chassis (sharing only the power cord) for a great price
hereIt also has several upgrades, including internal Crystal Cable wiring. The seller is the former Overkill distributor for the USA (and the current Crystal Cable distributor) and trust me he is MOTIVATED.
The new Overkill systems are using two separate 150A instead of the single chassis version. So this may be a unique piece but will still be serviced & repaired by Belles / Powermodules.
PS -- I think this amp can also be operated as a bridged two channel stereo amp with enormous power.