depends on the sub's ohm and watt ratings as well as the amp's ohm and watt ratings. connecting multiple subs to one amp in bridged mode either lowers or raises the ohm load(depanding on wiring) and allows you to get the maximum watts out of an amp. most if not all amps put out more power in mono mode vs. stereo mode and at lower ohm loads.
what subs do you have: how many VC and what ohms - watts (RMS and max)