If you look at the back panel of your amp, on the left side toward the bottom, you'll see it's maximum rated draw is 12 amps.
Your TV an sub should also have their max draw figures on them, so you can add them all together and see if they exceed 20 amps.
Note that the amp will only draw the full 12 amps when all seven channels are cranking at full power all at once. That's relatively unlikely, and even then, will probably not be more than a momentary event.