In theory, if the sub is built well, you would only notice more low frequencies from the rear channels. IIRC, Frequences below 100hZ, you can not tell where they are coming from. So, as long as it does not conflict with your main sub, it could enhance your bass. What I want to do, is have a sub similar to mine for each pair of speakers in my system. If I can get the room I want, that means 5 subs
I plan on a large room with a pair of speakers for each surround...totaling 8, so 4 subs in the back. I want to have the subs handle thelow frequencies and the speakers handle the mid and high frequencies. I doubt I will be able to find any more subs like the ones I have now, so, I will probably end up with the two I have for a while, till I get the subs for the rear.
My setup as it stands, is just an RCA splitter, from the sub out to the LFE input on my subs. It's 7.1 now, just split between two subs.
j