AT GSS we have the usual garden variety of classic mics and pres (251s, 47s, 67, r-122s etc and neve, api, osa, ua, v72, ). I have been curious about the brick esp given the price range (now that Fletcher has blessed it I will buy). I just used the Avalon DI on a session and was very pleased with it but I still prefer the DI on the OSA-L3 for bass most of the time (gotta love the lundahl tranny) esp with the Les Paul
I disagree with the idea that the 610 does not stack vox tracks well and distorts too easily. We love this pre for vox. It is a huge sounding pre and is not the "right" pre for everything. I will say the 2-610
on main vox and the v72a on backing vox has been a winning combo for several projects I have done recently. The EQ on the 2-610
can be magical with certain mic combos and performers.
As far as tube gear not having real "deep" bottom end I also disagree. The DI on the 2-610
is pretty darned deep in my opinion. Try putting a royer 122
a out in front of a nice kick (not in it) and through the pre and feel some thump. I am sure it lacks the slew rate of a solid state pre jacked up with crazy trannies (lundahl, richenbach or Bauer) but is not tubby or shallow to my ears. ok maybe a tad "hi-fi" ..god I hate having to use cliches like that..
In terms of track buildup residue I have not encountered any issues. I did track a recent project where we used the 2-610s on almost every track from acoustic guitars to vox to bass and even MS Matrix-ed the drums and had no issues. IMHO if anything exhibits this buildup characteristic it is often the older neve (include neve pretenders) and api stuff when it is pushed.
I find it helpful to run pre-recorded audio through the pres to get an idea of how they may color the sound. Many of my vintage pres really can sound great on mono sources and push them to the front but for the same reasons on stereo material they collapse the stereo image (distortion /phase/ demons / moons -planets in retrograde..are all factors).