Remember, all an amp is supposed to do is amplify sound. If you have crap equipment upstream feeding into the amp, you'll still have crap sound. Reread the first sentence.
I have always liked Onkyo equipment. I also think they are usually under rated by consumers. All the Onkyo amps/receivers I have heard put out a good sound provided you provide a nice signal going in. I had an early TX-4500MkII that surprised me it sounded so good. I was very happy with it for quite a few years.