I managed to solve my little sound card problem from the other day with my new frontend. Well, actually, I solved the problem of which box to use and what hardware to get at the same time. I just asked myself what would be the simplest, cheapest way to get something working, and the answer was to pick up a $15 SoundBlaster card at the used parts computer store ... so that's what I did.
I popped it in my amd64, and I already had most of myth installed, so I was up and running in no time. I lugged the little bugger into my bedroom, anxious to see how noisy it would be. It turns out that it was actually very quiet. I keep forgetting that I bought a really nice PSU a long time ago for the case (thanks, Josh), and it is near silent. In fact, hours later, I forgot it was on completely, and went to power it up only to find it was already running. So I might not even need to get a Mini for now.
I also picked up a USB sound device from Craigslist today for $10. I'm gonna try that on my Mini-ITX and see if there's any latency issues. Of course, that means building a new kernel and rebooting my box, and that makes me cranky. Rawr. No wanna touchy! Maybe I should look into using kexec.
Ah, so you did pick up a Seasonic PSU like I suggested? Right on!