Looking at a Mcintosh 275vi with upgraded gold lion tubes

Klipsch cornwalls iv's with an outstanding MC452. Looking to warm them up with more tube sound. Possibly bi-amp the two

I have used Gold Lion KT 88 in my Quicksilver monos and they have been great.  Reliable, sound good.    I bought a matched quad a few years back and they have many , many hours on them.   They are now spares but they had so many hours on them the silver getter flash was fading.   Tested stronger than spec for "new" when I got them and they still are pretty tightly matched, still reading just shy of "new"   

I have had GL KT 88, 77, 66 .... all reliable 

I have a 275 VI. I was disappointed with the sound using stock tubes. Make a long story short, I finally ended with winged C 6550s, Sylvania at7s, and telefunken ax7s. After these changes the amp sounds right with excellent, non cloudy bass, excellent detail, and very fine imaging. I have gotten the impression that some owners of the newer 275s are disappointed, but they might not be with better tubes.