You can measure this yourself if you want to.

Just wipe all of the music from your drives, and reboot with Hijack installed. Then surf to http://your.player/proc/meminfo and see how much is left over (MemFree+Buffers+Cached, I think).

This will be different between Mk1 and Mk2, as the software is different. And Mk2a should be exactly the same as Mk2, except 4MB more free.

-ml