Interestingly enough, I expected to have this problem with my system, using an ac97 sound chip. However, after all was setup and working, I had no problem using speakup and playing mp3's at the same time via the amp or mpg programs under the bash shell. I did have a 2GB processor, and 512MB of ram, so perhaps it is a resource issue for you? Also, I did not use the doubletalk, but the artic transport, so perhaps it's something in the doubletalk driver, though I would expect that particular synth to perform the best, since it has it's own processor on board.
