The 416s and the 415s have both been returned. Since then, I picked up a closely matched pair of 442s and a not-so-well-matched pair of 450s. The 450s are only marginally sweeter than the 447s, and the 442s are even less of an improvement. Neither pair has made a night and day difference, tone-wise. A rather fruitless venture, overall. I think I'm over experimenting with power tubes for a while.:| I achieved far more dramatic results when I went through my preamp toobz party phase...
...oh, why not....I'll share my findings/opinions with some 12ax7s I've tried....just in case anyone actually cares :wink:. For my C+'s preamp section, this is the best sounding lineup I've found thus far;
V1 = Telefunken ribbed plate (compared to all my other 12ax7s ---> somewhat decreased gain, bigger and more focused low end, increased aggression, great articulation, better tone...my favorite tube purchase ever, wish I had more...surprised I haven't seen anyone on here boasting about Telefunkens in their preamp sections)
V2, V3, V4 = Mesa Russian 2 (EH/Tungsol reissues...these have a bold punchy feel, not too gainy, and they maintain articulation very well)
V5 = Mesa Chinese square getter (these also sound great in my Mark III's V3 and V4 with Russian 2s for everything else)
Toobz that didn't make the cut = JJ, Sovtek WA, GT Chinese halo getter, Sovtek LPS (not even for V5), RCA black plate, and Tungsram (I see that a lot of blokes here really like Tungsrams in their Marks. Despite their rich beautiful swirly overtones, though, I find Tungsrams to be inarticulate and lacking in punch with Marks. Sounds better in my Chupacabra).