You have to edit the config file to get sound while retaining the 200mhz clockspeed (which is all you need for most games--everything I play on it). Open the file in the 'conf' folder with Wordpad, and find the place that says 'sound false.' Obviously, you want to change that to true, and sound will be enabled at 200mhz.
I don't know if the gngeo frontend, Rage2x, makes this easier or not.. never used it.