Newbie Question

I just purchased a 2/4 channel Pioneer Elite Amp m-72. I am currently running a VSX-41 Pioneer Elite receiver. I am attempting to get better musicality from my Mirage M890i towers. Their have two sets of terminals. Can I run two channels from the amp to one speaker and two to the other; of course observing polarity. This amp delivers 50 watts at 8 amps in this mode and 100 watts in two channel. The speakers call for 6 amps. Would it be better to just use stereo two channel wiring to this amp or would I get better performance the way I have spelled out above?

Lastly, could someone please explain to me "Bridging."

Thanks for your help if you can offer it.

Nick