1st, if they've got tweeters, they're probably not subwoofers, they're woofers. They will screw up your stoundstage really bad.

2nd, home theater subs aren't really set up to play music very well, they're set up for the effects for movies, so it wouldn't sound as good as it should even if they are subs.

3rd, home audio generally uses 8 ohm impedance drivers, so you're not going to get much power at all out of an amp that's set up for 4 ohm or even 2 ohm impedance.