If you are happy with the sound of 192kbps, then you can encode your music at this rate and you only need one copy of the music. This is where I started with my BeoPort, BS2 and BS3. When I really wanted to hear the best audio, I'd listen to the CD. As I've grown to use my BeoPort more (and my CDs less - it's a matter of convenience - my CDs are poorly organized), I've moved more of my music to lossless.
I first encode at 256kbps (MP3) and if I don't like the sound on my main system, I also encode a lossless file (and tell iTunes to only play the lossless, but send the mp3 to my BS2/BS3). Classical music I generally only encode as lossless because I rarely put it on the BS2/BS3, and I can definitely hear the difference with classical.
I agree that the BS6 is too small to hold more than a few lossless music files.
I'm considering the purchase of a BS5, and will probably encode most everything as lossless (except for my daughter's pop music). To me, it doesn't make sense to spend $6K on music player and then send it compressed files. On the other hand, if you cannot tell the difference, then why not?
Stan