Replacing home intercom system with in-wall speakers

[mugs]

I bought a house, and it came with a circa 1989 intercom/radio system. It's ugly and it's nothing spectacular, so I'm getting rid of it. I want to use the wires that originally went from the central unit to the room units to drive some in-wall speakers with the receiver in my family room. My wife likes being able to play the radio throughout the entire house.

Two problems:
1. The wiring from the intercom system is pretty thin - like 24-28 ga probably. I'm fine with the sound quality of the existing intercom system, so that doesn't bother me. What I'm concerned about is, is there any risk of starting a fire in my walls if my receiver puts too much current through the wire? I really have no idea what kind of voltage and amperage goes through speaker wires, but it's pretty thin wire and I want to be careful with my new house and all. Is there any kind of safety device (like a circuit breaker of sorts) that I could use to prevent an unsafe current from going through the wire?
2. Anyone have suggestions for where to buy volume knobs? Monoprice doesn't seem to sell them. I found them at Lowe's, but they want something like $35 apiece. It's basically a dimmer switch! I need to put a knob in each room so I can control the speakers individually.

 

[BigJ]

1) Honestly, I'd just replace the wire if you can. I don't know the specific ratings on your type of wire. Is it even jacketed? If it is, it should give you a maximum voltage rating and exact ga. In terms of protection if you can even use the wire, you'd be looking at what's called an In-Line Fuse. If you want specific answers, I'd consult with a Low-Voltage wiring expert.
2) Try partsexpress.com. They have a variety of volume controls starting at $20.