Well, if you asked me, the two best 6L6GC's being currently produced are the SED (used to be called Svetlana) and the JJ 6L6GC. I hear the TAD 6L6GC (TAD = Tube Amp Doctor) is pretty good as well.
I run either JJ's or SED 6L6GC's in my Mark IV or Triple Rectifier if I'm running 6L6GC's.
The JJ tends to run a bit cooler than the rest of the pack, but you can probably request a fairly set from www.eurotubes.com that will bias up properly in a Boogie. The JJ has more of a Gritty, ballsier vibe. When they are biased up fairly well, they tend to have a fattening effect in the power section and become a tad bit smoother. They're real rugged as well.
The SED 6L6GC has more of the old school NOS American 6L6GC vibe ala the GE, Sylvania/Philips. The tone is real sweet and smooth. They're not as deep as the JJ, but they make up for that with their sweet harmonic structure through the mids along with their bright, smooth high end.
The TAD 6L6GC, that a lot of folks seem to be talking about, is supposed to be close to the old Philips 7581A's. I have 2 matched Octets of the Philips 7581A's, but I haven't tried the TAD 6L6GC.
TAD also makes a 6L6wgc (5881) version. These have a good, smooth tone, but they can get kind of mushy while used in an amp with a lot of gain. I know that they don't like plate voltages in the 550 area as well. I haven't seen a Boogie with a plate voltage that high though. I ran them in my Triple Rectifier in the Bold/Tube Rectifier mode and the plate voltage is right in the 400 area. I've got a quad of these in my Twin Reverb and the plate voltage is right at 445 in that particular amp. I haven't tried them in a circuit with plate voltages between 450 and 550, so no comments there.
I would probably stick with the SED 6L6GC or the JJ 6L6GC. If you want to get the SED's from Mesa, they are the STR-454. They're 60 bux a pair. That's a lot of money. You can get a quad of them from www.kcanostubes.com for 70 bux that fall within the spec range for a Mesa/Boogie.
Dale
