If so, Monkey whould surely make such a compressor. I think there are indeed technical limitations on the compression. There is still some data to be compressed - and well, you cant put everything in nothing... But sometimes the monkey archieves compression ratios more than 50%, but thats still say 600 kb/sec.
I'd go for lossy - like musepack (you won't notice the difference, I'm sure... if you can, you have golden ears, which will be appreciated by the musepack developers - hehe

)
with mpc (you probably already know, but whatever :insane: ) you get 200 kb/sec, which is again 3 times smaller than lossless...
*edit - smiley didnt work out