I have used a Sony STRDB 1070 6 channel using internal amplifiers and as a prepro with a stack of 3 Onkyo M282s. No comparison. External amps made it sound much better.
I used an Onkyo TX DS 797 with its internal amps and as a prepro with external amps (Onkyo M504, Yamaha M80 and Kenwood KA9100). Sound quality much improved with external amps.
Ended up with an Integra processor, a single Onkyo Integra M504 and 3 Yamaha M80s. Sounded great.
In an effort to reduce my carbon footprint (not really) I swapped the Integra Processor for an Onkyo TXNR 1007 receiver but kept the M504 for main front L/R speakers (Thiel CS3.6s).
I think this is working but I have not sorted out the receiver yet.
