Lin, that one looks like it's going to be a beauty. My experience with Oncs and their relatives has been that they actually like quite a bit finer mix of medium than Cattleyas, Brassavola or Phals or the like. If you do re-pot I'd use something like small chunks of coconut coir mixed with perlite. I got a nice small bag of 1/4in chunk coir from Tropiflora a while back and although I do have to rinse it and soak before use, it's been excellent.
These orchids have much thinner roots than most others I grow, and also like to stay more moist, so when I buy one (usually from Trader Joe's
) that has all that sphagnum around it, and it is in bloom what I've done is just take a pair of chop sticks or sturdy tweezers and yanked some of the spaghnum out of the root ball - very carefully so as not to break roots. This at least creates some air spaces in there to let the roots breathe a bit while the blooming goes on. If I have a pot with holes handy, I will just drop the whole plant into the new pot and leave it be until the flowers are done, then go after more of the sphagnum with my chop sticks and replace medium with something chunkier but still pretty fine. If some roots are attached to pieces of moss I leave them be and just shake the new medium into the interior spaces as best I can. A little bit of moss in an orchid's pot that likes moisture isn't going to worry it, I don't think. I've had MUCH better luck doing this with my little Onc-sters.
You can get a pot from Lowe's or HD with some holes in it for that little lovely, and don't use their "usual" bagged bark mix for the new medium. It's much too coarse.