GC2 battery brands

I am replacing 2 Walmart group 27DC batteries that I got 6 years out of. They are just now starting to use some water in a couple cells. I would love to replace with AGM batteries, but not sure I can justify the cost of the batteries and some recommend that I should also replace my PD 9260C with a Boondocker converter to use with AGM. I am strongly leaning toward just getting 2 GC2 batteries from Sam's or similar and hope I get at least 4 years from them. I must say that I am very pleased to have gotten 6 years from the Wally batteries.

Thanks for all the information. Happy travels-- Mick