Personally I think the combination of that amp and the B&W 602 would be enough to put someone off music together. Whenever I have listened to those at hi-fi shows the immediate thing that strikes me is a dreadful harsh coloured sound, that perhaps people today assume is 'detail' and 'clarity', rather than the ear offending noise it is.
I know B&W are big advertizers so their products always review well, but you can also read between the lines. For instance a review will go on a length about how great the latest model is. When the next model comes out the reviewer then points out the boxy, compressed sound of the previous model having been eliminated in the latest super model that is great in every respect. This goes on ad infinitum.
Sorry OP but you have bought a typical screechy amp - lots of people do it, most amps are the same, nothing to be ashamed about. If you really want a decent transistor amp try RE Designs, and have a read of Positive Feedback to point in the right direction.
BTW the reason the amp is screechy is the design. It's a high-gain highly non-linear amp with bags of cross-over distortion, all made nice again by a whopping global negative feedback loop wrapped all the way around. Sadly that loop also acts as a harmonic multiplier so you get greater high odd-order harmonics (the ones that sound unpleasant) that you should, and the TIM (Transient intermodulation distortion) suffers as the internals of the amp puff and wheeze to keep the signal in check. They measure a low THD at 1kHz, but sound pretty ropey.
With a class A you lose the cross-over distortion - the main reason they sound better. You also tend to be biasing the deviced in a more linear region - another reason they sound better. Then class A tends to draw a continuous power from the PSU, so the PSU doesn't have to play the music like in a class B, so you remove most of the PSU from the music. Ironically the more linear an amp is, the less bad effects GNFB has on it too, so you will also win there. Tube amps have similar clear physical reasons why they sound better but I'll not go into that here.