thanks guys.
@szadzik as far as I can tell, the Octave isn't balanced, so that's out for me, I've implemented my beta22 as balanced input/output only. With regard to AmpCity, they may be a touch expensive, but they are offering a UK-based warranty and a 30-day trial period, which for me makes the extra worth it over an overseas supplier.
@Duckman SBTouch (with soundcheck's toolkit software mods and sigma11 linear psu) will be the transport via coax. I think the beta22 won't do much to colour the sound one way or the other, but to my ears, the LCD-2 sounds best with a solidly neutral source, so that may be an overall good synergy, especially if the soundstage is big and open.
I think I'll go for it - worst-case if I don't like it I can return it within 30 days. I'll also be running it out unbalanced through a Bottlehead Crack into DT770 600ohm, so that might give an impression of what it sounds like through some tubey goodness.