Recommend 12V mono amp please

[mfaughn]

I would like to know if there is an inexpensive solution(s) that will serve my needs. DIY or finished product is fine.

I have an efficient omnidirectional speaker (made by SoundSphere) that I like hang up at outdoor parties. It is mono. Sometimes the only power is from a car so 12V power is preferable to other voltages. Audio source is usually an ipod-like thing with the stereo signal summed to mono using a few resistors.

Most of the amps I find that run on 12V are stereo. I'm wondering if there is a mono solution that would give me more power than one channel of one of the stereo amps.

I tried running the speaker off my modest subwoofer amp from my car ipod thing plugged into the low level inputs (normally connected to head-unit) and it didn't work. Don't know why, maybe not high enough voltage from digital audio player. A car amp isn't ideal though because its more of a pain to run it from 120V than would be a t-amp sort of thing with a wall wart/brick.

Thanks for any suggestions.