Follow-up... here are some of the potential issues I see:

1. RoadRunner might get in the way. I know I can default mplayerc (the video player for RR) to output to a specific sound card. However, I'm worried RR won't allow playing MP3's and videos at the same time. I've got dualmon option turned on for dual monitor support, and it continues to play videos when I exit the video player to use other functions, but as soon as I go into another "media related" function (FM tuner, MP3 player), it stops the video. Maybe when I get a second sound card, this will go away. Otherwise, I'll have to figure out how to tweak RR to work around this issue.