Kasha Rockmod II questions (also Enlg 840/50)

[O D]

I purchased a Rockmod II and i must say it sounds absolutely fantastic. That is, through the poweramp of a Line6 Flextone II. When i plug it into my Engl 840/50, it sounds like, well, {censored}. The lows are flabby, the highs are screechy and the mids "papery". I think the Groove Tubes 5881/6l6 power tubes might be at fault, since i experienced similar sounds with the Rocktron Piranha, altough not to the same extent. Is the Rockmod simply not suited for 6L6 tubes, does the Engl have a weird voicing (other users chime in) or are Groove Tubes simply a load of crap?

I need to replace the tubes in the Rockmod II. Do any Rockmod users have tips as to which tubes work well with the preamp? Also, starting from top left, what are the roles of V1, V2, V3,V4 and V5?

 

Thanks!