I am merely running two amps in order to power two sets of speakers. The Motion 40's can handle 300 Watts and the C298 offers up 340 Watts at 4 ohms. The 35Xti's spec 250 Watts with the 375BEE maxing out at 250 Watts. My preamp, the Rogue RP-1, has 60 steps in 1 db increments and we typically listen to music around 30 db, so I figure the output is about 50% per amp.
Hence, the 40's typically are getting about 170 Watts while the 35's receive about 125 Watts. Both amps have gain settings, so one speaker is not louder than the other, but the 35Xti/375BEE certainly does add "sparkle" which the 40/C298 duo cannot match. So each speaker is getting just the right amount of power during play in order for them to sound their best..it is a fair amount of power without the creation of any discernable heat.
In the past if you ran 295 Watts of power for 3 hours the heat would be unbearable. While the D-class amp does not have the refined sound as the A/B amp, it serves the purpose of doing what the 35Xti's cannot do: create solid bass waves while filling up the lower midrange frequencies.
It is worthy to note that when listening to music - even with the amps running 50% of power - we can have conversations in normal voice tones, even across the room. What I have learned - and took some time to figure out - is that good interconnects and cables, a better set of output tubes - as well as room dampening - give the sound a tonal quality that takes the edge off the music that motivates one to "turn it down". As time goes by, the music has settled quite a bit and I expect that the volume will go up a few more db in the future because of the "settling in" factor. It is real and generally follows a "bloom".
Not for the faint of heart, this journey has taken a good 10 years and probably close to 15K in funds. My wife was resistant, but has since come around and now provides me with a daily set list.