Distorted or what?
Are you sure it's not a crossover problem that is hidden by your Marantzes tone controls or lower power?
Or is it a failing tweeter/too bright?
What are you using for speakers? Have you checked your speakers out? Are they correctly rated for the output, ohms, power and all?
If your woofers are going to have problems with an amp, the tweeters will suffer first I'd bet and tweeters in bookshelf speakers are rarely rated above 40W because they need very little power to reproduce efficiently compared to woofers and midranges.
And do you really want an audio-video integrated/receiver or dedicated stereo setup with a decoder for another amp and a center/sub?
The problem may be that some people don't dig AV stuff for 'musicality', whatever that is...
My old Onkyo DR-90 had a built in CD/DVD player and Dolby 5.1/DTS and was really nice in stereo mode for CDs, records and tapes but it's biggest weakness in the end was the chip amps, and the same side blew twice.
The NIN CD I had (The Downward Spiral) was some really fun s--- on it though