If they are over rated, then why do OEMs invest in AGM batteries in their Auto Stop/Start versions of their cars?
If they didn't work better, they wouldn't spend the money to put them in those vehicles.
I bought this one:
NSB-AGM 94R/L4
I keep it alive with this:
CTEK Multi US 7002 - CTEK Battery ChargersCTEK Battery Chargers
Two years in, so far, so good. Car sits a lot.
Good luck.