It is not only about SQ, more importantly proper and sensible design and therefore reliability.
This is the inside of an 11.2 channel Marantz SR 8012 AVR.
Note the puny amp boards crowded onto two heat sinks, 6 on one side and five on the other. No room for decent output transistors all crowded round the power transformer.
Now lets take the Marantz 7705 pre/pro.
This is much more open with no major sources of heat, that runs cool with a maximum power consumption of only 60 watts.
That is a much better prospect.
This allows for the use of decent amps with one heat sink per amp and large triple output stage with six output transistors per channel. Now you are talking decent amps.
Lastly I don't think it acceptable in this day and age have 11 power amps on doing nothing. With separates you can switch in only the amps being used. If it is two channel listening then just the front left and right amps. Others can be switched in as required.