Bi-amping Rules

Unless you have the exact model for both amps, don't bother.  If you're contemplating a purchase of 2 like amps...getting 1 good amp for a side  is better than 2 lesser ones...and certainly better than different models.

I passively Bi amp my Maggie 3.6's with a pair of David Berning ZH270 power amps. The result is much better sound from my  Maggies then using one amp. In fact I won't get 3.7's because with there series crossover you can't bi amp. I also when I was upgrating one of my bernings I thru a vtl ST80 in to replace one berning and it sounded just as good. One nice things about the Berning amps is they have volume controls so I can adjust bass/mid levels versus the treble level. 
Alan

Thanks for all the inputs. I have experimented bi-amping my Aerius i  using few different amps, all SS, and could never get it to sound right or better than a single (good) amp.

Kalali, my dealer recommended a pair of Aesthetix Atlas stereo amp for vertical bi-amping.  It's a hybrid amp with a built in crossover. 

I am working on a plan to try them out in next month or so. 

Agree with those who say that you really have to have an active bi-amp system for it to make much sense.  Some benefits can be achieved with a passive vertical bi-amp which of course assumes you are using two identical amps.  Otherwise, you need an active crossover.  In my system, active crossover low passes the bass below about 8O hz to a high power class D stereo amp then to a pair of 10" woofers for each channel; and high passes the mids and highs to a tube amp that drives the (almost) full range drivers. This does introduce lots of complexity and requires lots of outlets and cables.  The system to my ears sounds wonderful but there are many places for gremlins to rear their ugly little heads, which per Murphy, happens on occasion. 

In my case, the music I listen to does not have an overwhelming amount of very low bass content so most of the information is reproduced by the tube amp.  The class D amp is really for all practical purposes, a sub-woofer amp and in fact, the active crossover I use (NHT X-1) was designed primarily to use ahead of a subwoofer.