Tubes for Sonic Frontiers Line 1?

I am looking for some suggestions for tubes to try with my Line 1. I have tried the stock Sovtek (too "thin", not warm in the mids) and Amperex white label (bugle boy types) 6dj8 (too week in the bass but good in the mids, clear and more expansive sound than Sovtek or my Classe CP-50). I would like something like the Amperex but with the full bass I get from my CP-50.
Thanks