Stereo wiring help

Have a Kenwood KAC 8401 640 watt 4 channel amp that came installed on the boat. Originally had a set of Mako MB Quartz on the tower. Those were sold and I installed a set of double bullet speakers from Monster Tower. The original wiring is connected to channel A left and right with the subwoofer bridged on channel b. After I run another set of speaker wires, will it hurt the amp or speakers to leave the amp bridged on channel b and hook the second set to channel b left and right? I don't have the $$$ for another amp for the sub right now, but don't want to do any damage. Thanks in advance for helping a electrical dumbass.

Definitely don't want to run components on the same channel as a sub, it'll rob the sub's power as well as keeping you from being able to properly configure gains/crossover settings, as well as possibly having conflicting impedance loads, which all together will turn things sour pretty quickly.

What new speakers are you adding? Just some in-deck mids? 2-ch amps with less than 100w of power are pretty cheap.