The Trader Joe's seem to be all in potting compost of some kind. I've waited until the stop flowering and then repotted. The root ball is dense and getting all the old material out is a chore. I used the sprayer form the kitchen sink for some. One I sprayed as much as I could out and then repotted whole. Others I've broken open the root ball from the center, the center is a little less dense.
I don't have a preferred media. i have never repotted an orchid before. But I think my local orchid club sells media. i will likely rejoin the club again, but not until I come back from a two week trip.