The lower the first number, the higher up it is on the Marantz food chain.
The SA (Super Audio) 1 was their top model about 15 years ago. It listed for $7500. Then the SA-7S1, which came out about 8 years ago, and list for $6500. Then the SA-11S1, which came out about 10 years ago and listed for $3500. It was followed up by the S2 version, and currently is in the SA-11 S3 version listing for $4000.
Look through the Audiogon Bluebook, you don't have to have a subscription. It will tell you model numbers, their release date, and original list price.
