By cleanest; of course, I mean highest headroom and dynamic punch. I need a matched quad of 'em to replace the TAD 6L6WGCs that came in my TopHat Ambassador 100. I borrowed the RCA Blackplates out of my Showman head, temporarily and they're nice, but I want something even cleaner sounding. I'm running a 12AT7 at the phase inverter I'm looking online right now at these for comparison: SED 6L6 (these are compared to the large bottle Sylvanias..) GT 6L6-CHP( black plates w/ heat sink wings) GT 6L6-S(Slovakian made .. higher power,aggressive dynamic tone) Also considering the TAD 6L6GC-STR because they're compared to the RCA Blackplates .. but I'm wondering if the other tubes I mentioned are quite a bit cleaner ? Any experiences with these ?