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

My setup is: I own a stereo integrated amp rated at 90wpc into 8 ohms. My speakers require more power than my integrated can adequately deliver at higher volumes. My intent was to buy a new separate power amp to connect to the pre-outs of my integrated so I could at least utilize the pre-amp section of the integrated, saving myself the expense of replacing it with a separate pre-amp. I asked the distributor of my integrated for pre-out specs so I could properly match it to a new separate power amp (I've read that the power amp input impedance should be at least 10k times that of the pre-amp output impedance). But instead of providing the requested specs, he suggested I purchase a new stereo power amp from him. One which is an exact duplicate as the power amp section in my integrated. Then use the two stereo amps (one stereo integrated and one stereo power amp) in a monoblock configuration: one channel from the stereo integrated amp dedicated to one speaker; and one channel from the separate stereo power amp dedicated to the other speaker - so each channel is driven by a different amp. He suggested that would provide each channel with 180 watts of power into 8 ohms, since only one channel was being loaded per amp. Is this clearer?

John - Thank you for the detailed explanation. It is much help. The proposition sounded goofy to me too. I cannot insert an external crossover for my mains as my integrated does not have any power inputs, therefore the mains run full-range. I am pleased with the dynamics of my system and usually do not require higher volumes. But sometimes I do, like when I play rock. So it would be nice to have some extra power on occasion.
The second (power) amp is a duplicate of the power section that is in my integrated.
As you suggested, I think I'll be better off just getting a more desireable power amp. A new power amp would then also provide the capability of inserting a crossover to ease the demand of my main speakers. Thanks again.

And just for the record ... I misunderstood my dealer's suggestion completely! A follow-up contact with him revealed that he meant for me to simply bi-amp my speakers (which I cannot do since my speakers have only one set of binding posts). So all of this confusion was for not. I am the Mayor of Stupidville. And for my punishment I will dump my current system and get a Bose Wave Radio ;>}