I wrote the reply last night after midnight. This morning I note two things: I have no idea how it really works - it just does. And two, you can use default with the .asoundrc above since it aliases it to nforce... you don't have to specify nforce, although obviously you can if you want.
Well, after rebooting last night, the above no longer works. I have no idea why it did, or why it quit. Obviously something else was going on, and I have yet to figure out what actually made things work for a while.