Should be possible,,,,,,,
Just a gut feel though. You will need to run the serial port pretty much pedal to the metal and then have a fairly good sized queue behind it so that you can even out the serial port byte rate against the data rate you feed the DAC. Under any circumstances the byte rate over the serial port has to be faster overall than the rate you would feed data to the DAC.

In addition, If you find out that it is necessary to do any conversion of the wave file data in order to get it into a format suitable for the DAC I would do that conversion on the PC side before sending the data down the serial port. That said though, if you were using a 12 bit DAC instead of an 8 bit one then in order to improve bandwidth on the serial port you would like to send two 12 bit samples packed in 3 serial data stream bytes.

Michael Karas