Larry, I also own a Cary SLI-80. I spent big bucks rolling NOS tubes in it. Final compliment: Amperex USA 'pinched waist' 6922s; Syl. USN issue 6SN7WGTAs (selected for tight triode matching); GEC KT-88s and Mullard 5AS4s. The Eico HF-89 that I recently restored and 'tweaked' runs rings around the Cary. More bass, more space, better flow, and better detail. Back-up singers and choruses sound like individual voices seperated in space blending without any 'gritty' distortion. Granted the only thing vintage about the amp now are the tubes and iron (and the basic circuit topology). But on the other hand, the Cary is basically a modern execution of a 1950s design. BTW my linestage is a modern take on what is basically a 1930s WE design (differential class A parallel feed). I guess the point I am trying to makew is: most modern tube stuff are based on designs that have been around for awhile. Where you see a lot of improvement is in the quality of the small parts (caps, resistors, wire, etc.) used.
