I my younger days I spent countless hours looking over amplifier schematics. Its how I learned all the electronics symbols and how circuits worked in real life applications.
Once I figured out how the amplifiers worked it became easy for me to boost them for much higher running power both by raising the supply rail voltages and building up the output stages and current handling components.
Drop the output ohms capacity to under .5 ohms. WOW does that give you some punch! your speakers reactance is not always 4 ohms, most amplifiers have a current limiting sytem to keep them stable durring the low ohms points in a speakers power draw.
hense the 8-4-2 ohm ratings.
(this can beat up a cheap speaker rather fast though)
I ran Profile brand amplilfiers. I liked them because they had good sound, simple rugged circuits and could easily be boosted to run at double their factory ratings! Bugged the crap out of the guys with the big name stuff to get walked all over by a middle class brand powered system.
And yes they would over heat and shut down rather fast! The other guys just did not need to know that part!
Learn your electronics! Electronics nerd pays well!
And sinse you were so nice about everything heres 3 amp IC spec sheets, Plus that 170 w is not obsolete! Digikey caries it for around $15 and these other 3 are in there catalog as well for around $15 each.
have fun!