I would give them a shot. I have no experience with scubamax, but my thought is if the big-ticket gear items they sell aren't on your shopping list, maybe they've got some of the smaller ones where brand is totally irrelevant that you do want/need. I'd give them a chance to get established and get their foot in the door with the larger brands before writing them off, however given some time if they don't start stocking other brands, I might think twice.
The brands that a shop chooses to stock CAN say something about the shop, though, in this case I don't think it does. A shop near me recently became a national distributor for a brand that is almost unheard of in north america and dropped a few of the more recognized brands at the same time. They heavily promote that brand and walking into their shop is like walking into a showroom for that brand, though they do sell some Aqualung stuff still. To me, this doesn't encourage customer loyalty, it says "we'll take your money" because if you buy it, even if the customer service sucks, you have to go back because you can't go anywhere else to get your gear serviced.
The brands that a shop chooses to stock CAN say something about the shop, though, in this case I don't think it does. A shop near me recently became a national distributor for a brand that is almost unheard of in north america and dropped a few of the more recognized brands at the same time. They heavily promote that brand and walking into their shop is like walking into a showroom for that brand, though they do sell some Aqualung stuff still. To me, this doesn't encourage customer loyalty, it says "we'll take your money" because if you buy it, even if the customer service sucks, you have to go back because you can't go anywhere else to get your gear serviced.