Have you considered Polypaudio:

http://0pointer.de/lennart/projects/polypaudio/

The Ubuntu people are looing at replacing ESD with this one. In their scheme, Polypaudio would use ALSA's dmix rather than direct ALSA.

polypaudio is a sound server for Linux and other Unix like operating systems. It is intended to be an improved drop-in replacement for the Enlightened Sound Daemon (ESOUND).«