I have Beoport and Win Media Center PC connected, but not with a BS 3.
I think I know where you are heading, as the same thought occured to me. I think the music could be loaded onto a SD card with a reader, as I was able to accomplish a download with Sony Memory Pro Duo reader. The Sony card then plays CD's (somewhat) in the car, and on my camera ( also limited). I do not like tha gaps and pauses that occur.
Interestingly enough, I can unload music from the PC Media Center (some of which came off my BS 3200 ) via Bluetooth onto my PDA SD card. By that logic I should be able to upload music files to an MP3 device and play them back through a BS 1. Might just be quicker than burning a CD, and hold more music, but the CD is still the best solution so far.