I've got a PRS-600 and an M-Edge Executive case for it. I also have the M-Edge e-Luminator light. This combination was rated as the best case and light for the PRS-600 on several e-reader sites. I just bought my daughter a PRS-650 after checking with M-Edge to see if they'd make an Executive case for it. They said they were plannning on it.
Now they are renegging and saying they are waiting to gauge if there is sufficient interest to warrant a new case development. This is the same company that makes multiple cases for every combination of Kindle and iPad.
I think this is lame and sad. If anyone is interested in a good case for their PRS-650 take a look at the M-Edge Executive cases and contact their support folks at:
http://www.medgestore.com/about/contact/
The Executive cases for the PRS-600 are at:
http://www.medgestore.com/products/prs600-executive.psp
Thanks.