The Svet EL34''s are nice tubes - stick with them; matched Mullards will be an expensive road. Its hard for me to believe someone can't hear the difference between a WE300B and, say, a Golden Dragon or Sovtek or...Some Mullard tubes sound mushy, rolled, etc., some don't. Any gas leaks don't help. I've liked the Mullard 12AU7 iterations, but thought other Mullard inputs sounded, as some have said, veiled. Go with twl's recommendation on the 12AT7's; he's right about the Phillips (upper mid glare, strident highs). As for your 70/70 purchase, its a push-pull single ended design (hence, your 70 or so watts) tubed on the outputs with Golden Dragon 300B in stock unit. Because VAC is the distributor for Golden Dragon (GD) this is understandable, and, although the unit is designed around the GD deficiencies, you can do much better than the GD in that amp. I can't remember if it has individual tube biasing, but I think it relies on close matching instead. Again, this is understandable given that VAC controls the GD tube, but if you want to do better, the expense of purchasing 8 (four per side?) matched new production WE300B's becomes, at $2000 ($495 per matched pair on audiogon new, assuming you can then match that pair to the others...), um, problematic. So, no WE300B in 70/70 unless you own an oil well. That's a limitation. Do look into other 300B iterations instead of the GD though (does Svet have their act together on one yet, or did they dump that idea?). But, because of expense, ask around with guys like twl before 300B re-tubing. Get a good amp stand or isolation platform also for the 70/70.
