It can be done but you need to preamps/volume controls.
the first preamp needs two outputs. One would go to the less powerful amp and then one would go to the second preamp/volume control then out to the more powerful amp. This way you could adjust the balance with the second preamp then use the first one as a master.
For what it is worth my local shop was playing around and use a MC275 and MC7200 to byamp a pair or 805D3s. I did not listen in extreme detail but it sounded nice on the surface.