Interesting.
I've moved mine on. It sounded great at low levels, but when it came to gigging volumes there was something lacking for me. i can't put my finger on it, but despite trying all the things I've read, I just couldn't get the kind of 'grunt' out of it I get from my Ashdown MAG 400 (485W @ 4 Ohm UK built).
I've also moved on the Laney VC30 as I really don't play much guitar any more.
However, if it works for you, I'm delighted. I defo. found that the Mullard made a difference.
I'm very interested in the MiBass.
G.