Ahh, i see what you mean now...What you may want to consider is setting up a "holding" tank that can be filled with tap water...It doesnt have to be pretty, a stock tank from a feed store would work. Adding a filter system with seeded media would eliminate the ammonia...Add a heater to have it at the right temp...You could hide it in the basement somewhere and that way you would always have water available, at a fraction of the cost.
Exactly how hard is hard? Once again, unless you are keeping wild caught stock, the gh and kh isnt a big deal for most tropical fish...