You're not far from me at all. I'm at the xroads of 295/95/195.
*****'s water is pretty good, at least near me. They use a Marineland Saltwater Dispenser and they keep it at SG 1.025. I know because I bought my Yellow Tang from them and it's one of the best specimens I've seen. I think they use Instant Ocean as their mix so if you are running reef, you need additives for CA, etc.
I run a RO unit from my kitchen sink for convenience with 3 gallon tank. I also have a RO/DI that fills my 55G drum when I do big water changes. As for mixing up the salt, you can use it as soon as all salt is dissolved, pH stabilized (30 mins usually), and temp is adequate (depends on how much you made). Having it ready a day or 2 in advance is just being cautious, which isn't a bad thing.
If you need any help, I'm not that far. I usually go down towards Hidden Reef since it's closer than Trop is for me. Alquatics in Hamilton isn't bad either and worth a look if you come by that way.