Making a non-sub console into a sub console

[TheBoogieman]

Any sub under 10" isn't really a sub, it's just a speaker with very limited bass.

 

[lexbrooks]

I've done a crash course on amplifiers powering speakers.
Looks like either the stereo or an amp will power the 4 speakers up front and on top, then have a bridged amp power the subwoofer separately in mono.
That's about as far as I've gotten.