Upgrading from Integrated Amp to Separates

Where did ANYBODY say BAT was DARK?
OP is asking for opinions and EXPERIENCES.
MY experience with BAT was that it really was good, however in my system in my room to my ears the Lyngdorf 2170 was much superior.
Obviously YMMV.

The first thing that jumped to mind when you mentioned finesse and more power is combining a tubed preamp with a Class-A solid state amp.  Not sure if you're looking new or used, but if the latter pairing something like an Allnic L3000 pre with a Plinius SA103 or Clayton S100 amp could be a sublime mix of nuance,warmth, and natural detail with excellent imaging and soundstaging -- and plenty of power.  If you'd prefer a tube amp maybe a VAC Phi 200 or ARC Ref 75se or 150 among others. 

If you're buying new I'd recommend a Sachs SP14 preamp with the Clayton S100, but not really sure on higher-powered tube amps in this price range.  Anyway, best of luck. 

I have no experience with Lyngdorf, but I can vouch for Neal at Sound Science as being a great guy to work with.   While I'd like to try the Lyngdorf all in one solution, I'm hung up on the nostalgia and sound of tube amps.

I've owned 40.1's on an off for about 7 years (currently on again).  I've tried several integrateds and three preamps, with the Aesthetix Calypso Signature being my favorite.

If memory serves me correct, I tried two SS amps... Bryston 4BST and Plinius SA-102.   Both were decent as far as solid state goes, with Plinius getting the nod, but SS just never sounds as rewarding  to me as a good tube amp.

There have been many good tube amps I've owned with my 40.1's...

Current amps (highly recommended):

• VAC 30/30 Signature - only 32 WPC, but very high current and plenty powerful for my listening pleasure.  Great with female vocals, acoustic and jazz.  I originally owned this amp as a standard MKIII, sold it, then in the last six months found a MK III Signature and snatched it up.  I plan on keeping this amp a long time.
• Music Reference RM9 MK2 - euphonic midrange and my preferred amp for rock.   Fun amp that makes everything sound good.

Other great to good tube amps:

• VAC 70/70 Signature - this amp is difficult to come by.   Similar to the 30/30, but puts out twice the wattage.  Great for jazz, female vocals, classical and acoustic.  If it didn't weigh 135 pounds, I'd still own this beast.
• McIntosh MC275 MKV - great, spunky all-around amp.   Not many of the MK V's are available on the used market, probably for good reason.  I'd own this amp again.
• VAC PHI 200 - has the best bass of any tube amp I've ever owned, but lacks the finesse, micro dynamics and midrange of the other aforementioned amps 

Not Recommended:

• CJ Premier 140 - sounds nothing like a tube amp.  I would go with a SS amp before I'd buy this amp again.
• McIntosh MA2275 tube integrated - great looking amp.   I really wanted to like this amp because it looks so cool, but it sounded underpowered, soft and flat.  
• Musical Fidelity M3 NuVista - just bad.

Uberwalt if you read auxinputs post you would know why I said BAT is not dark. 

Allnic  makes a couple of tube integrated amps. One I believe is the T-2000 now with k150 tubes about 100 watts. Very nice gear.