Question For Those In The Know About Audio Research Power Amps

I've flirted with ARC gear over the years, owning an LS5 preamp some years ago but never trying their power amps.

I've always had the idea that ARC tube power was a little lean and sterile and not in the Conrad Johnson style of presentation, with tube bloominess and that glorious CJ midrange.

Of course, I realize not all ARC amps sound the same and that some are warmer and more tube-like than others.

Anyway, I recently purchased an ARC Reference 110 SE, and really like a lot about what it does. Stage depth and imaging are excellent, it's detailed and dynamic. As if to reinforce the negative stereotype, it is a little on the lean side, but not horribly so. It's a musical amp overall, and that's what counts.

Questions -
1 - this was sold to me as a "SE" model, which I understood to mean that it was modified to allow the use of KT150's, which my amp has. Was this an 'official' factory modification, and if so, is the SE designation something which can be used when I try to resell the amp? I can't seem to find others running KT150's referring to their amp as the 'SE'. Or is the SE designation relating to a different upgrade altogether? 

2 - is this 'SE' amp backwards compatible with any other tube types?

2 - what's the next model up from the Ref 110 that might exhibit a little more tube bloom (warmth) than the  Ref 110? I wouldn't want to lose the wonderful transparency and soundstage ability of this unit, but if it could be fleshed out a little more then that would be a plus. The amp is only a couple weeks old, to me, so I'm still trying cables and supports etc, to see if there's more to be had, but I would say at this stage that this is a pretty amazing amp.

Any insights would be appreciated!

Thanks
Rooze