Sorry you haven't had any replies, but I could add some general comments about AGMs that might help.
AGMs are probably not going to be the best buy.
Some brands have thin plates and can only be used as starter batteries whereas others have very thick plates, like traction batteries, for deep cycle use. True Deep Cycle AGMs are expensive and not so easy to source but they are now becoming more popular, but there are only a few designed for marine
use. The problem is that not all AGMs are designed to be discharged 50% or more and then not recharged to 100% almost immediately. Many cheaper ones are designed for Telecoms or Solar
standby use, not for mounting in a boat which often falls off 3 metre waves, so check very carefully with the manufacturer that they are rugged enough. AGMs main advantage is they can charge much faster and accept higher charging
currents, but not all brands make these claims, so potential new buyers are often confused. Some people on these forums
have had bad experiences with AGMs - but maybe they have bought the wrong type. My expensive Lifeline AGMs are in their 10th year!