Hi Rlw3,
I owned ACT 2 and upgraded to GAT about a year ago. i have not heard ACT 2 s2, but have owned CJ for well over a dozen years straight so have some reasonable familiarity with the sound, and also nearly upgraded to s2...so spoke with many people.
Compared with ACT2:
- one enormous difference is treble...the ACT 2 actually sounds hard and strident in comparison. i heard it when i first bought aCT2...but quickly adjusted. But i NEVER realized how hard it would be in comparison to GAT which is 25-30% more detailed, but 100% more natural, fulsome and yet clear.
- Noise floor is next...supremely quiet. I have 95db speakers and not a whisper when the unit is at a deafening 60 with no signal coming thru. Ear within 7 inches of tweeter.
- This gives a more transparent sense of space, detail...but it also allows the natural CJ tonal beauty to come thru without sounding 'laden' with golden hue...this is in my experience a true first for CJ at this extreme level of performance. Incredibly clear but still with far more natural CJ beauty than ACT2.
- Next, the overall balance of the unit is better in terms of even delivery across spectrum. 20% better?
- Extension in treble is better, and bass (very good in ACT2) is probably 15% lower with definition
- Words of advice: power cables matters less here than on other products, and u will need to seriously step up to improve on the stock cable. i do use PAD Dominus. EAT Tube dampers are a MUST...the stock Electroharmonix can get noise...i use Amperex 6922 PQ US White label. Finally, try using HRS nimbus couplers/damper...also big improvement. This a tremendous unit outta the box...these are just improvements for your consideration.
my two cents. ask if any other questions. good luck.