I decided to try the RCA Lyra. It's a USB-based 900MHz transmitter / receiver that seems to be fairly well received. They're apparently being discontinued, so you can find them very inexpensively (Google or message me for info on 2 sites I know that have it for roughly the same price). One downside I've heard is it requires MusicMatch for plug-n-play compatability, but apparently other systems (iTunes for example) can be made to work with this.
I ordered a transmitter/receiver with 2 extra receivers (to use in the workshop and backyard) and spent a total of ~$35 shipped. I don't expect miracles, but I'm keeping my fingers crossed. At the very least, I hope to use it as a stopgap until I decide what technology to go with for this type of service down the road.