How are you acclimatizing? Yes, it's stressful, but it's easy to mitigate the some of the shock. It's no different that any other fish store in terms of hardness, pH, even salinity (as other stores dose salt in the fresh water aquariums).
Given that, you do have to be sure that the fish you buy there will work with tap water. For example: Ottos cannot survive in Tucson tap water. I'd recommend taking a sample of your tank water to the store and ask Ben to test it and have him recommend fish that would survive in your parameters. He also sells RO water for $0.50 a gallon.
I'd probably sell it too if someone couldn't afford his prices- weekly water changes can be expensive. There are also RO filters available for sale on craigslist- I purchased mine for $20 (spent $10 fixing it up and 2 hours reworking the horribly incorrect plumbing).