A simple word of warning - not all AGMs are the same!
Doesn't matter who they are made by it's the job they are designed to do that's important. Duracell AGMs are Automotive batteries, and are probably stater batteries which will give a high discharge current
and a fast charge rate, but not designed to go regularly down to 50% SoC. Lifeline also do starter AGM
batteries and other companies make Telecom standby AGMs.
Too many people buy the wrong kind of AGMs and then post on here what a waste of money