Hi Ray,
Check out the review from Jeff Dorgay, who apparently did not wish to upgrade to ART 3...but he did find the GAT more compelling as i understand, having spoken with him. GAT better than both it seems. (i have never heard the ART 3). I did not find ACT 2 as sensitive to HRS/without HRS as the GAT. I wonder if 6N30P tube is less microphonic than 6922? Cannot say.