Of course any dealer is going to say newer is better - he needs to make a living.
I have hade my cj ART3 for about 5 weeks now and I asked Lew at cj his thoughts of the GAT were before I bought the ART3.
One main difference was that the GAT has SS output to enable very low output impedance and back to 6922's for the gain. thank god for that.
In real life very few cables have issues with the ART3. I have yet to use one that has issues in driving speakers. I think the specs of low ouput impedance might be more " specs driven importance" for some audiophiles in ASIA.
Lew felt that the GAT was perhaps a little better, however due to the monoblock nature of the ART, it does have more substantial power supplies and is still a COST NO OBJECT design.
Lew is a very straight shooter and not partial to exaggerating, he also said he uses the ART3 at home.
Anyway, he said the GAT is very much better than the ACT series 2 which is more of the comparison cj market, cj are aiming for as there are so small numbers of ART.
my view, try to find a older Art series 1 or series 2 and upgrade it to ART3 and be happy for a very long time.
If not I am sure the GAT will be very nice and a return to form for cj after the ACT2
Me I am even tossing up whether to sell my ART1 or use it for a 2nd system
cheers