today DIY Audio Amp building is about being a electronics hobbyist - not about "superior sound" or cost saving
a point to consider is that it is arguable that power amps for audio are pretty much a solved problem - researchers in Psychoacoustics don't believe there are differences worth bother with between basically competent audio amplifiers
the Journal of the Audio Engineering Society had many amplifier articles 1970-80's, very few since
Dr Geddes researched, published listening test results for his "GedLee Metric" - and bought ~$200 Pioneer audio amps at Costco to demo his ~$4K each speakers
DIY for better sound involves speakers, speaker directivity/location, room treatment - not the electronics
transparent electronics mass manufactured usually cost much less than hobbyists can buy just the raw parts for - often less than a DIY hobbyist would have to spend on power supply or case alone
http://www.cordellaudio.com/book/ and Pass books are both really somewhat advanced - you really need to be solid on the basics of circuits to get much from them - very good for an EE wanting to quickly get up to speed on audio amps