I use this on my 150 cc Chinese Knock off.... Good sound for the size... I run my MP3 player right to it with an RCA adapter from Radio Shack... It powers a pair of 5" speakers and is loud enough that I can hear it even when ramping up... Runs about $40
http://www.davidnavone.com/cart.asp?24&cat=5
Size: 1.5" x 3.00" x 4.00"
Output Power @ 14.4 Volts DC: 20 Watts x 20 Watts
(Peak Power: 150 Watts x 150 Watts)
THD + Noise: Less than 0.1%
S/N: Greater than 90 dB
Channel Separation: Greater than 55 dB
Frequency Response: 20 Hz to 20 kHz