[camaraderie]

The 25amp draw is MUCH higher than the 20hr. amp draw and can in no way be compared. Example...a typical group 31 battery rated at 100ah's at the 20 hour rate uses a draw of 5amps for 20 hours. Increasing the draw to 25 amps dramatically reduces the amphours available.
Example:
Trojan group31 25amp rating is 190 minutes...79 amp hours. At the 20 hour rate it provides 110ah's...almost 40% more. BUT...this is a TRUE deep cycle battery...not a hybrid starting/deepcycle...so you are probably looking at less of an increase with your Interstates Mike.
Assuming your 160 minute reserve # is at 25amps..the 66amp hours gc1111 quotes might convert to 80-90 amp hours at the 20 hour rate. As such I am thinking you have a group 27 battery?