Ben Jacoby is excellent but a bit our of the way in Brooklyn. I'n in Manhattan, Need someone to troubleshoot and repair a noisy left channel. Would consider a serious hobbiest whose adjusted the plate voltage of the driver tubes (assuming that's the issue) Just replaced the 4 driver tubes and the power tubes seem fine.
You live in Manhattan but Brooklyn is out of the way? You'd let a amateur who you don't know work on a $6000 amplifier? Maybe you should just ship it back to Audio Research or would that be too inconvenient?
I would try Stereo Exchange. They're on Broadway between Bleecker and Houston. They sell ARC and have a service department right in the store. Overall, I don't care for the store, but they're service department is very good.