So they have an "extra firm" version of the foam as well (260 lbs+ riders)... The Corbin I had on my EX500 was pretty doggone firm but actually was better that way- I wonder if opting for the extra-firm would give a similar result?
I too had a seat done by Spencer's, for a C-10 Concours. It at least made the stock seat bearable, but I doubt I'd do it again for my V-Strom. Seat Concepts does sound interesting though.
Gone but not forgotten:
2006 EX500, "Sport-Touring Lite"