[cr0sh]

If there's cat5 at the keypads back to the central hub, and the speaker wires go to the keypads, then you can just hook the wires from the speakers to the cat5 - choose one or two pair (depending on the distance, you might want to "double up" to lower the impedance over the run), and hook 'em up. Then you just need to figure out a distribution system at the central hub location.

If you find you can run the speakers on a single pair per speaker - that will leave you with 2 other pairs on the cat5 - which you could use for control or communication.

But what I would do before all of that is try to reverse-engineer the protocols or whatnot that the whole system is currently using, so you can keep the keypads/amps and such, and create some kind of custom main "head unit" later.