If you're constantly buying distilled, you will probably reach the point where it would've been cheaper just to get a little RO system. I got mine from someone on this board upgrading theirs - it's just a little 35 gallon-per-day unit, but it was very cheap and is very effective.
Using IO salt is akin to being a slumlord to some people, but I'm not a salt snob - I use it in mine, and I haven't had any problems with LPS, softies, or zoas.