Boy, that is a tough choice then, but generally, you get what you pay for. My brother used to be the district manager for S. CA Petco's and he said it varies wildly on the death rates of fish depending on who took care of the fish at each store. Hopefully your buddies are in the good category. I've never had a fish die inside a warranty so I don't really consider it. I just watch the fish for a while before I buy them to make sure they are acting normally, and don't have any Ich or anything.
I'd say go ahead and add some plants.
Wouldn't you like to beside the seaside?