A subwoofer is no different to any other speaker, it is just optimised for playing low notes.
Therefore it doesn't need 'power', just a signal, exactly the same as any other speaker.
So, wire up your amplifier with a permanent live, quality earth and remote (to switch the amp on and off) and then connect your speakers (including the subwoofer) in the normal fashion.
I'll happily draw you a wiring diagram if you need it - any help you need, give me a shout