2 stereo amps in a mono-block config = 2 x power?

I wish to double the power of my system. I have a stereo integrated amp with two sets of pre-outs. One set of pre-outs is connected to my sub. The amp manufacturer offers the power amp portion in my integrated as a stand-alone stereo power amp. If I drive one channel with my integrated, and connect the other channel via one pre-out into one channel of the stand-alone, will I effectively be doubling my power? I cannot bi-amp in the traditional sense, as my speakers have only one set of binding posts. Also, by keeping the one interconnect to the stand-alone amp as short as possible, will I be introducing problems with coherency between the two speakers (time and phase) or cause other problems?