I have owned a lot of Modwright gear but never this integrated. For his other gear that uses 6922 variants, I like tubes that are more honest and transparent with sparkle, as by default Modwright has a warmer sonic signature. The honesty allows the electronics to reclaim a bit of speed and focus I felt might otherwise be lacking.
My favorite ones I've tried are Amperex 6DJ8 with white lettering (not Bugle Boys), made in Holland. Closely behind them, I actually really enjoyed Reflektor 6N23P-EV, which I bought from Viva Tubes:
I've tried others from Sylvania, Mullard, Genelex, etc, and these two stood out. The Reflektor is not as revealing as the Amperex but still had wonderful harmonics. Stock JJ are meh, so you will be thrilled in the sonic upgrade from whatever tubes you land!