Reference preamp with laid back and relaxed highs

my experience suggests you will not find such a preamp in production in 2008. coloration is what most designers try to avoid.

consider vintage preamps, such as cj, mfa, and audio research. you have more information and experience than most of us, so you are probably aware of the usual suspects, i.e., products of the 80's and 70's. it is possible that you don't want to go there. if that is the case, perhaps you could consider shindo preamps. i have not heard them, but, if i were searching for a current preamp, i would want to hear one.

just one more thing. i have never found lamm products particularly warm or tube like in the classic sense. i have auditioned many systems using lamm amps and preamps. with the exception of one, they have sounded closer to truth than beauty. the one exception was lamm with tannoy speakers at a stereophile show in ny about 4 years ago.

This suggestion maybe from left field,I personally really like the Cello preamps,they all come with balanced outputs but they are fischer,which may require a custom cable atleast on the output of the preamp.Down side they are hard to find in good condition,however the sound is fantastic,

Few that exhibit such a coloration in the upper middle range & treble incorporated 2A3 R-ing tube ( I just sold such a preamp to a friend of mine - very sweet. However, it needed some work & tube rolling to get the best out of it. I didn't want to bother. ) could be coincidence....It will be very difficult to find (100%) what you are looking for. When you are going to find the closest match , you could possibly placed it in the hands of trusted modder/technician to fine-tune it to your taste(or)needs.

Esoteric Audio Research 864 or maybe the newer 868, I owned the 864, with two tubes in the line stage 1 x 12au7, 1 x 12AX7.
Rolling the 12AU7 made it very versatile to "tune" to your system, but its transformer ins AND outs were never anything less than right in the zone, quite relaxed, not limpid and the highs were exceptionally smooth without reticence.
Price is a bargain anyway you look at it...plus you get the legendary EAR phono stage thrown in !!!
They show up here with some frequency, one just sold for under 2K....good luck

Tvad, I enjoy the Boulder 2010 for specific qualities that you are looking for. It is the most relaxed and neutral preamp I have ever heard. Good luck and enjoy the search.