Welcome to the forum.
If you are buying fish locally, and the store uses the same tap water that you do, then the fish you list will be fine, no need to stress over the hardness....
Personally, I'd add 2 filters to that tank, one on each end...that way, if one fails, you have a backup...plus you can stagger your filter cleaning schedule, and always have a filter running...I'm a big fan of the AC's, I'd put 2 AC30's on the tank, 60G worth of filtration, 3X the volume of your water.
You don't need the carbon that comes with the filters, and I don't even use the sponges, either...I make additional bags of ceramic media for my HOB's, and in the space where the sponge would go, I just use cheap poly batting that can be found at WalMart....add a fresh piece each week during WC's, and toss the old piece...no nasty sponges to clean all of the time...