I like your pictures... Your tank looks nice. What do you use for lighting? I am also fairly new to the hobby; and I do have a few tidbits of advice, so you might want to take it with a grain of salt
First off, through my research I found that you almost cannot have enough water flow in a tank... I have a 29 gallon tank and I have 3 sources of water movement producing over 600 gallons per hour in circulation... And I can tell you that the more current you have going over and through your live rock the better!
Also I was wondering about your cycling time? You say you added the live rock on November 6th? How long was the tank set up before that? I hope the tank has cycled sufficiently since those fish are all expensive!! I cycled my tank with hermit crabs, live rock, and live sand for a month.
As for your filtration, I would say add a protein skimmer before you buy another filter... The live rock should serve as your biological filtration and a skimmer can take care of the rest... I myself am in the same boat... I started off with a Fluval 205 cannister because that's what I had along with a small Aquaclear, but my next filtration purchase will be a protein skimmer.
And finally, with regard to fish stocking remember that it's usually best to add the less aggressive fish first so they can gain a territory before the stronger, more aggressive fish are introduced. I think yellow tangs are supposed to be very aggressive fish, hopefully he doesn't pick on any less aggressive fish you add down the road.
Well I hope I could help you!