If you're looking for hifi quality, search for things like Naim Audio (be careful though, the schematics you can find on the net, aren't entirely correct), diyAudio.com have some nice ideas and Mr. Leach did some nice work too.
There is one interesting design from LC Audio “the End Millennium”, has been an article series about the power amp in a Swedish audio mag and did get great results then. Could not find the schematics online at an English site, only Danish but attached it…