you really think that's the reason? i always thought the reason was that the 400+ was kind of an albatross with 12 6L6's powering it. i think they publicly say that's the reason, but i'm sure nobody enjoys having to replace power tubes in the 400+.
That is RIDICULOUS. Why not run 6 KT77s instead?
I think solid state / hybrid / tube debate is much less of an issue with bass gear because really, only solid state distortion is an artifice. The cleans really aren't that bad, ESPECIALLY with a good instrument and a good set of speakers. If you want a clean, punchy MODERN tone solid state delivers the power in spades without prohibitive cost, weight, or even maintenance. I really think that I would pick tube or diode, depending on what the gig required.
, but, viva la differance!