majhi:
A transistor, you say? Pardon the noob-ness, but if I need multiple channels to operate each light independently, wouldn't a transistor not work? From my understanding (which is more than likely very wrong), isn't a transistor limited to a single throughput?
You would need multiple transistors just as you would need multiple relays; both devices can act as a switch, the primary difference with relays is electrical isolation.
Hell most relays are driven with a transistor anyway.