what pre amp for ATC SCM 40v2 spkrs + 250.5 Pass Labs pwr amp

I see thank you for the further insight. 
So then I kindly ask which SS pre-amps are you aware that meet these ideals that you mentioned earlier? 

Ayre !!!!!

I've been really pleased with how well my VAC Ren MKV preamp pairs with my Pass XA30.8 amp, and hence picked Ralph's brain a bit about whether the preamp design lends itself towards good compatibility - including excellent and tight bass extension.  From the sounds of it, the VAC's transformer- coupled Class A1 balanced triode design is likely responsible for a large piece of the synergy.  I feel the combo is giving me a flavor of the best of SS/tube integration.

Thanks for your input @three_easy_payments, 
which model @tomic601 ? and what kind of system are you running?

my systems are visible on the virtual system page. The reference is an ARC REF5se preamp that while it does not meet the balanced standard that Ralph cites, make decent sound. It drives a 6 m length of Audioquest WEL cable effortlessly into Vandersteen M7 HPA amplifiers. I have used an inexpensive mogami set of XLR wire also with excellent sonic and low noise results.

I have spent more than a few hours listening to the Ayre KX-R preamp and it is an incredible bit of SS engineering. I have owned an Ayre power amp in the past and currently own and use in a recording studio an Ayre A2D converter - anything Ayre touch sounds good and is hyper well engineered.

just my two cents.

Ralph of course makes great gear also!