When I get the AHB2 in monoWhen you do this the "sound quality" not the loudness will deteriorate. As when any amp is bridged, the there are many negatives that happen, one is that will be here is the ability to drive low impedances and the stability into low impedances. Look at the impedance graph of the 3.7's, it's nasty. If you need more watt's get a bigger amp.
https://www.stereophile.com/images/archivesart/1208T37fig1.jpg
Cheers George