I had a series 2 S/300 ( same era ) and there was a slight upgrade at the time but nothing major. It was also a time that they raised the purchase price . I think the more important thing about either would be how well it was taken care of and the actual condition of either unit.Either will get the job done fine,depending on condition....The "S" series amps were and are considered some of the best amps around for that era....
