If you want a really good explanation of the differences between the 400's and the new 500's, call Alan Goodwin in Boston.
He's a Spectral "expert" with tons of technical information.
I speak with Terry often. He's now living in California with his wife and doing fine.
He has a new cell phone number (the old one was an Overature cell phone)
Terry says that Alan Goodwin (in Mass.) is now the go-to-guy for Spectral.
You can email Terry at: tmenacker@gmail.com