Let me take a stab at this one.

I have an Onkyo 906 which is rated at 145w x 7. It has a "massive toroidal transformer." I put this in quotations because that is what Onkyo boasts. I now use the Onkyo as a pre/pro waiting to purchase a (guess what). The 906 now just runs my surround backs.

My main power drive is the 7500. I did a bit of research and found the 7500 in a test review to have been bench tested at 240wpc ALL CHANNELS DRIVEN at Outlaw's .03 THD rating. In short the 7500 throws down the hammer like a Veyron. If you have seen the transformers on the 7500/7700 amps they are truly MASSIVE in a massive way. The 7700, which you are inquiring about, makes the toroidal transformer on my 906 look like my Acura TL's (a nice car) 3.2l v6 engine which compares to the 7500's power plant which is likened to a Lamborghini Aventador. Ok so the Veyron is the 7900 but you get the message.

There is no way that my Onkyo can produce the 145 x 7 all channels driven. The 906 AVR can probably push no more than 80wpc all channels driven at best and probably more like 65 to 70wpc. The AVR I own has 4 output devices per channel, the 7500/7700 have 12 output devices per channel. Compare the 18000mf total capacitance of the 7 channel Onkyo 906 to the 210000mf capacitance of the 7 channel 7700. Compare the amount of heatsink on a flagship AVR to the amound of heatsink on these amps per channel. The 906 has a heatsink that serves all channels. The 7500/7700 have heatsinks that serve EACH channel. In short the 7700 is a multichannel monoblock.

The damping factor, which controls the dynamic suspension of the speaker drivers, is huge on the amps but small on the AVRs. I can take the powerful 906 AVR and easily run it to it's limit on powerful program material. The 7700 will have practically UNLIMITED power. No matter how hard you may want to drive it, the 7700 will perform with the specified .03 THD and that is every channel firing at once. Even when one or two channels are firing the AVRs will run out of breath and heat up. Not so for the amps which if you remember have huge reserves via "bottomless pit" capacitance.

Buy the 7700 and report back how you have NO REGRETS.

All the best.