When you open the compartment that holds the RAM backup battery, you have access to a 4 Gig USB drive that performs the Hard Drive functions when no hard drive is installed. Over on the Korg USA forum a couple of guys talked about having replaced that USB drive with 16 and 32 Gig drives. I have no idea what impact that might have on the Warrantee but it would certainly be cheaper than a hard drive.

With access to three USB drives (one in front, one in back, and one in the hard drive compartment) there is a lot of memory available.