In 1990 I listened to a system in a Hafler rep's 280ZX. It used a single MSE40di amp (rated at 20w RMS x 2 into 4 ohms) to drive the complete system, a total of 15 speakers. It was impressive as hell, had great volume and SQ, but the passive crossover assortment was a bit of a nightmare. I always intended to build a smaller version of that system in a Triumph Spitfire.
BTW, when you say speakers and monoblock, I assume you're talking subwoofers. That would work. If you're going to run an entire system off a single amp, you'd need a 2 channel amp to have stereo.