The way I look at it these days, Class A (many tube or some SS amps, very inefficient) or Class D are the two pure approaches to consider at each end of the power consumption spectrum. Then there is Class A/B which most SS amps are, that prior to Class D was teh technology used to improve power consumption and retain "quality sound" Some will argue Class A/B is a compromise approach ( I might tend to agree) that might still yield very good results but not as easily or as often as Class A.
IMHO, in general, these days, I would rather go with either Class A or Class D amps for pure sound quality. Either done well and matched to the right gear can deliver top notch performance, subject still to personal tastes as always.
Class D is fairly mature these days and offers a nice bundle of value and performance in a small package that will appeal to many.
Class A amps, will tend to be larger and cost more to operate but some may still see the value if its "that sound" they like and cannot find elsewhere.
