My Dual Rec shipped with the Chinese 6L6's, (*STR 440), they sound really good for a stock Mesa tube.
I have tried JJ KT77's in it, they sound good but took about 10 hours to break in before they lost some of their harshness.
I have Ruby EL34's in it now and I think these are GREAT tubes for the Rectos. They don't have as much bottom as the KT77s or the JJ E34Ls but the Recto has Massive amounts of bottom anyway so you are not going to miss it. I find that if I dial in Too much bottom or scoop the mids too much, it is easier to lose definition in the mix of a band.
I have a Lonestar Classic that shipped with STR 430's, (*Sovteks) and I think this is one of the most lifeless tubes that Mesa has ever rebranded. I even called Tech Support and complained. I have SED 6L6's in it now and they are WORLDS better for sound quality, chime, harmonics, drive and volume. Mesa should take the STR 430's and digs a big hole and bury them to keep anyone from actually buying or using them ever again. Total CRAP!!!