I ran the ACT2.2 for a couple of years. I enjoyed it immensely but it was always a little too cold/neutral for my tastes and a wee bit hot in the treble. Still a fabulous amp though and one you could live with for good if forced to. That said I have heard the wondeful majestic ART3 before and would have that in preference. More emotion, more music.
I now have the GAT though and would take that over both of the above. It was quite a large step up from the Act series 2, a step that I wasn't expecting tbh. In fact, I would say its a very different amplifier ... more of everything in the way you'd expect but a lot more natural sounding and with more warmth and lower mid/upper bass fullness but not in a manner that subtracts from dynamics, speed or accuracy. The coherence and unravelling ability it brought to the table was also pretty spellbinding, so much so that it made the ACT2.2 sound a bit muddled with certain allbums.
I now have the GAT though and would take that over both of the above. It was quite a large step up from the Act series 2, a step that I wasn't expecting tbh. In fact, I would say its a very different amplifier ... more of everything in the way you'd expect but a lot more natural sounding and with more warmth and lower mid/upper bass fullness but not in a manner that subtracts from dynamics, speed or accuracy. The coherence and unravelling ability it brought to the table was also pretty spellbinding, so much so that it made the ACT2.2 sound a bit muddled with certain allbums.