Not even close to max. If you read Franklink's review of the Standard, I believe it details getting around 45 ft lb in 22 which should translate to about 30 in 177. My own standard barrel does not shoot the 16.1s very well, so that much power isn't too useful unless you plan to try 13.4 or 15 gn slugs. By going to the 23" polygonal barrel, it can drive the 16.1s and heavier slugs more easily. Ours can do over 40 ft lb with the 20.5 gn NSA's and we normally run the 16.1s at 33 ft lb.
If you're asking how much power it will generate by going up in caliber, it's more but may be limited by what valve and frame port it has. 177 Standard's are typically much smaller porting but CAN be drilled to 25 cal spec as I've done on a couple. It has to be very carefully done as the valve seal support gets pretty thin for the 25.
Bob