Oops. I was thinking CLARINET. Subwoofer can use speaker level input from the paramours. Arguably, most folks do it the other way, trying to find a line level output from preamp to go to sub. You could do Y-adapters to do so. The interesting thing about using speaker levels as a sub input, is that the signal passes through the main amplifier and gets the needed phase shifts to integrate better with the rest of the spectrum. Yes, there is a little added noise, but for the most part should be insignificant. Getting a smooth transition is often difficult.
jh