I bought a, I guess it's a switch decoder, off a guy in Canada. It uses one proportional channel but gives me 8 on/off's and works on Spektrum radios. Paid like $80 or $90 for it.
I'm going to be picking up one of those cheap Chinese 2.4ghz radios, I've found a few threads on them and they seem to have a pretty good following and work well. But you could get 2 for $50 and have 8 proportional channels and 4 aux channels. Plus you can program mixing on your computer via software.
http://www.hobbyking.com/hobbyking/s..._Rx_V2_(Mode_2)