Trojan T-105's are good batteries. GC-2 class. True DEEP CYCLE Flooded wet.
So what are the advantages to switching to AGM (SInce you were considering AGM)
Total life: No advantage there. Average life for AGM and well maintained Flooded wet not much different and in my expierence. Wet did better. but that's my test.
Total capacity: Same.. Identical in fact.
You don't water AGM.. This may be why mine did not last as long.
PROFIT for the store/manufacturer.. OH yes. Big advantage there. Store/Maker make much more profit due to far far far higher price.
Now. in some few cases the fact they are "Low gassing' may be important. but if you are set up for flooded wet then the battery compartment is properly vented so this does not apply.
and in some cases the "no this side up" feature may be important. but again. NOT in your case.
So.. My suggestion: Do not waste money on AGM.