The problem I think we're running into right now is, your questions have been answered many times before, and then we're pointing you at the info, and you seem to want your specific questions answered before reading up on what's been previously covered. You asked if there was a thread.
Interfacing an amp to the HiFi system is the same regardless of how many amps you are adding.
I asked you if you had a budget, if you were cool with just the underseat woofers, if you were installing it yourself, and what part of the country you were in. You haven't answered any of those questions. That would be a good place to start, and I would suggest doing it in a new thread, by the way
