I can second your reccommendation of Steve Huntley and GNS on yet another front: Steve was also employed by ARC for some years before moving over to Wadia. GNS also does extensive upgrading to many ARC components. I sent my ARC LS-2B pre-amp in to Steve for his "Standard" level upgrade (a "Reference" level is also available). I was delighted with the sound when it was returned but always wondered about my judgement being impaired by the lack of anything else to compare it to, the time that had passed since I last heard it, and the mind-games we all play when we've invested money into an improvement like that. Well, a few weeks ago I had the opportunity to A/B my modified LS-2B with a bone-stock LS-2B my friend uses in his system. We used a matched pair of Telefunken 6922's (actually these ones were made by Mullard). We were doing the comparison at my friends place and his system is all high-end Levinsion gear, great IC's, PC's and NHT 3.3's in a nice listening room. Guess what? No mind games here! Both of us immediately noted the improvements...it wasn't just subtle either. The most immediate differences were in clarity and focus (both improved with the GNS modified pre). Soundstage was marginally wider with the GNS mod. Overall it was $750 very well spent in both of our opinions. Steve was very straight foward to deal with (easier to reach on the phone than by email, though he did respond both ways). Turnaround was a bit slow, but they did warn me they were backed up at the time. Still, I don't think it was more than 3-weeks. Definitely reccommended!
http://www.greatnorthernsound.com
http://www.greatnorthernsound.com