Hi ZZ,
I got mine last xmas . It's got the original operating system 4 b & I think 5.4 ? eprom. I didn't update to 4 c.

I don't know how many mb's it loads on start up, again it's original sounds. I did play around with wav audio loops for styles & got that working. Even created a clarinet from the wav samples in a soundfont. Didn't sound as good as the onboard clarinet, but that may have been due to my lack of knowledge on how to manipulate the sample once it was loaded ie add effects etc etc I took the samples etc back out.
About the only thing I've added is a few user styles which I created for my Making Styles group, and they're only convervisions from other keyboards or or made using the copy function.
Unlike you, I haven't got the musical talent to create from scratch.

AJ's stuff sounds interesting..

best wishes
rikki