The thing you want to watch with a TNT200 is the DC pulse on power up. This WILL demag dynamic speakers over time.
Best to leave it powered on all the time.
This is not a guess, I had 2 TNT200's for several years.
Best sounding used SS amp under $500, IMHO. Blows the newer Hafler's (i.e. 9500) away.
Replace the coupling caps with some MIT PPFX for a real suprise!