MY opinion is, get a better subwoofer than the 5T. Yes, the acoustimass is garbage. It can't even be called a subwoofer, I don't believe Bose ever claimed it was a true subwoofer, which is why they always called it a "bass module", maybe they want to avoid legal trouble from false advertising.
But the 5T is pretty weak also, at least on paper. It's extension only goes to 35 hertz. It has a 10" driver powered by a 100 watt amp. Even at its $300 introductory price, it is still no bargain. There are a lot better $300 subs out there, I would look at the BIC Acoustech PL-200, or the BIC Acoustech H100, or the BIC America VK12, BIC seems to have the best entry level subs. Also the Hsu Research STF1 is on sale right now for $250, and while it doesn't go that deep, there is no tighter subwoofer in it's price class. Something else to look at that has extension and tightness is the STF2. I think any of these subs will be far superior to the EMP 5t sub.
One other thing, you may not think you had cause to get a sub before, but how do you know what you were missing if you weren't hearing it? Even older recordings may surprise you.