Hmm. I went from like 15 years of marine fish only to reefs within the last year, so I feel pretty equipped to handle this question....I'll try to summarize my experience here anyway.
1. I also started with PC's, I soon realized that if I wanted to keep anything really cool I had to upgrade. There are many options for that...more PC's, VHO's, etc. I ended up installing a couple of metal halides that do fine. This may seem like a ghastly expense, but can be done relatively cheaply of you shop around for while and are not afraid to use a pair of wire strippers. I can give ya some really good starts in that regard.
2. Forget about the traditional mean of biological treatment. i.e. cut out your wet/dry, fluidized bed, what ever you’re using. Don't even think about an under gravel.. All you need from here on out is live rock, circulation, and skimmers.
3. Oh yeah, cut way the hell back on fish livestock and feeding.
4. You don't need all of those supplements, most seawater is nutrient deficient, keep it that way.
Other than that, its pretty much the same 8)
Mushrooms are pretty tough, xenia was my first coral...they are pretty demanding of water quality as I killed my first few, but nonetheless, a good candidate. I really had good success with yellow star polyps early on and grew them quite well in the refugium on my fish only tank. Star polyps are also good in the sense that you propagate them quite easily by slicing off a layer and gluing it to peace of coral.
Good luck and welcome aboard.