Designing good power amplifiers is not at all easy, particularly if it is all discrete components.
There is biasing of the preamp and driver transistors, maximizing linearity of the amplifier before feedback is applied, biasing the output stage to minimize crossover distortion and have it remain correctly biased as the transistors heat up, Stability after feed back is applied into capacitive and inductive loads, avoiding enough output offset to put significant DC current into the speakers. And then there are the enhancements live output short circuit protection. Not sure it can be done without experience and a lot of calculation.
Anyway, this might be a place to start:
http://english.cxem.net/amplifier/amplifier4.phpAnd this link is interesting because it has a lot of comments on the design of a popular ETI-466 power amplifier, including links to the articles and schematics.
http://home.alphalink.com.au/~cambie/ETI466Web.htmRichard.