I realise this is a bit late for the original post but I've just come across this thread.

I own Model Solutions of Canada Ltd. and we make very high performance SFX6 sound modules that are fully configurable, you can download your own sounds to them, have an enormous (40Watts) amount of output power (on 26Volts) - 10Watts on 12V. Plus they play back at full CD sound quality and have two fully proportional throttle controlled engine sounds. These new SFX6 modules will be out of the assembly plant about July 22nd, 2009.

Regards,
David Harrison
CEO
Model Solutions of Canada Ltd.
[link=http://www.modelsolutions.ca]www.modelsolutions.ca[/link]