Those USB sound cards are just a very cheap and easy way of adding audio zones, and you control it like you would an MD. I have one for my bathroom speakers, one for my garden speakers, and one for my guitar amp. They are brilliant considering it means you can do away with an entire MD and its associated gubbins if audio is all you need.
An it looks like I can use the one 7.1 card to run four different stereo channels. That's pretty cool. I don't have a need for it yet, but cool nonetheless.
I don't use Pandora (not sure I really know what it is), but why don't you have a look at adding some internet radio stations and playing those through your new USB sound card.
I used the script to install my local Internet radio stations. It's really cool, but I like the customizable and commercial-free streaming of Pandora. I wish I could explicitly connect to a channel that I create in pandora like a normal Internet Radio station.
I have a bunch of friends and colleagues coming over for a Poker game on Thursday. I was hoping to have enough buttoned up by then. One of them is a programmer who has tons of media. If I can get him interested, maybe he'd join in with LMCE development.