The potting medium that you end up choosing should ultimately reflect your watering habits. If you tend to water sparingly, pot your 'chid up with spaghnum moss because it retains water/moisture a lot longer than other mediums. But since the issue has been root rot, I think it'd be better off in a fir/charcoal mix...something that allows better drainage and air circulation to the roots so they dry out a bit in between waterings. By using a more open medium like this, it will help prevent root rot from reoccurring. I use the regular "Orchid Mix" by Schultz, from Lowes or Home Depot and it works fine for me. Another thing you might want to consider is repotting in a clear plastic pot, because it allows you to look into the medium and better judge whether the plant needs watering.

oops....forgot to mention...pertaining to the clear pots, you don't need to buy them online. This may sound silly, but whenever I go to Starbucks and get an iced drink, I save the clear plastic cup that it comes in, punch holes in the bottom, and presto - instant orchid pot!! :)