Maybe this has been asked a thousand times:
(if yes, pls forgive the mpc rookie...)

Can anyone recommend some test samples to verify the quality enhancement of mpc over lame compressed mp3 files?
I've done some test comparing some mpc-files (quality 6) and lame mp3 (--alt-preset extreme) and couldn't hear any difference (at least in my samples).

..:: sundance ::..

maybe you'll find some here
http://sjeng.sourceforge.net/ftp/vorbis/

From the FAQ:

Test samples
HydrogenAudio's directory
Other pages
Flac decoder for encoded test samples

It might be a good idea to do a search for lame problem samples.