To be honest, I would probably recommend Alchemy. I guess it depends a little bit on what you are doing. Alchemy is a far more powerful tool, but Diskmaker does a couple of unique things.
Diskmaker is not a program that we are doing a lot of current development on. We originally designed it as a tool to take sounds from SampleCell (first version) and from the old Kurzweil 250 and convert them into useable sounds for the K2000. It does a very good job at this and it really is the ONLY way to take sounds from the K250 or SampleCell 1 and keep the different sample mappings intact. Diskmaker translates the complete keyboard setup - all of the samples (PLUS the basic envelope settings on the K250) - not just raw samples and turns them into finished, keymapped K2000 programs.
Saying all of this, we designed the program over 4 years ago when there was NO practical way to get samples into the K2000 (you couldn't even get the sampler option for quite awhile). Since then, Alchemy has been re-released and the K2000 can now support AIFF transfers. I now believe Diskmaker is mainly important if you have a large K250 library you want to convert.