It doesn't matter, sub Amps go from 100 All the way up
to 1000! Good Range is 100 to 300. Depends on size of sub etc.
Ask in subwoofer forum. they'll need a $budget and your Room size.
Some decent subs can be had for $300 or less.
Don't forget, powered sub (amp is built-in)
and speaker level inputs!!!
Anthem MRX-300-Outlaw Audio M2200
Rythmik F12 subs
Paradigm Signature S6,C1,S1
Harman Kardon DMC1000 (music)
Assassin HTPC (movies)