I already read almost all TDA family high power monolithic amplifier and all of datasheet require feedback gain on less than 24dB(or 30dB. What reason so we must implement it and what the drawback if i used this ic to act as unity gain buffer amp?

 

What was or what is the best IC amplifier manufacturer?

I think that National Semocinductor has a good range of IC amplifiers up to
80W of power.