I am pretty sure I saw at least one post on a slimserver thread about a person that was doing exactly what you want to do.

Although the Squeezebox is $299, the new Duet which is basically a squeezebox with no display and no IR output jack, is around $149 if you do not buy the Jive controller. I guess in that case it is not a Duet but a Singlet.

I feel the loss of the IR output jack is a big negative for the following reason. Lets say you want to put the player (squeezebox) in some room (in my house it is the master bedroom) and connect it to a small stereo rig so you can hear the music. My rig is not small but then again it is about 30 years old and I will match its audio against almost anything out there today) You can tell the slimserver to have the Player (squeezebox) output up to 4 IR commands (power on, power off, volume up, volume down,) when the matching event happens. You connect/tape an IR emitter to your receiver and give slimserver the correct IR patterns and you are done. Whenever one of the 4 events happens for any reason (Web interface, Jive controller, 9400, 9600 . . . ) the correct IR will be sent. I felt that was one of the neatest integration featores, and it is now gone, or it costs $150 to get it back.

Actually you only need the power commands as the player will handle the volume sent to the receiver over the analog channel.