I can't find the post anymore, but I could swear I read something a year or two ago posted by the empeg guys that explicitly stated that rotational speed made little if any difference.

I don't believe that you'll see any difference in boot times, as the vast majority of the boot process is done from flash ram, and not the hard drive at all.

Are you having a problem with song access times? The only time you should see any delay is when you change songs; any other time, the empeg player software should be anticipating what it needs to load and do it just before it needs it. I can't say that I've ever had to wait any more than a fraction of a second even when selecting new stuff, though.