Some excellent notes of the 6SN7 family of tubes(and their presentations), most of which I can verify from personal experience, having tried all the top contenders: (http://home.att.net/~chimeraone/6sn7sound.html) Contact Kevin at Upscale regarding the Popes. (http://www.upscaleaudio.com/Pope-6SN7GT_p_105.html) He'll never steer you wrong, and his quality control/testing/matching is exemplary. BTW- The 6SN7s in your Cary are used as buffers, and a quad of bottom gettered Sylvania 6SN7GT/VT-231s, from the 50's (ie: http://cgi.ebay.com/Sylvania-6SN7GT-Bad-Boy-Tubes-Matched-Pair_W0QQitemZ260453877957QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item3ca442c8c5&_trksid=p3286.c0.m14) would serve you well, at somewhat less of a price. I'm not vouching for that seller, as I've never purchased from him.
