As you can probably guess I'm a bit of a Cornford fan, I've had a few of these but the MK50H is the best IMO. I stuffed some Yellow Jackets & JJ's in mine the other day, and it sounded really good. I think that it showed me that my Sovtek 5881WXT's are at the end of there best. So, now I need some new 5881's, but I'm confused what to get: 6L6's, 5881WXT, 5881, NOS, some sellers have them graded for hotter, or cooler. What I want are some good quality valves that'll bring out the best from my lovely amp. I do find that it can be a little over-emphasised low down at the moment. I use mine with 2x12 V30 closed back cab. To me the MK50H does lovely cleans, and great fat distorted blues/rock whilst still retaining clarity and richness. I cannot afford to get fancy tubes these days, so NOS Tung Sol's are out. What would you get, Cornford still use the Sovtek 5881WXT's, are these the best? I may swap out a few preamp tubes to, so again what would you use?