Hi Tyler,
I apologize I didn't answer you sooner, I've been a little tied down at work. Let me first welcome you to the board.
And I'm very happy that Incysor and my brother Dragon have contributed to your questions before me.
I will give you advice on best practices that have worked for me:
If you can avoid mixing LPS and SPS corals do so. The main reason is size of the tank and the fact that they require space and different water flows; Incysor touched on that nicely.
Your tank needs to have a theme, either SPS or LPS. OKay if you decide SPS, it can be done but requires more lighting. The MH is the preferred method and there is a mod out there with the MH ready for your tank; I just don't remember the thread.
You can however get away with power compacts like me; I run four 24watt PC and a 13 watt fuge light under my 12 gallon cube.
You may purchase the T-5 Actnics and daisy chain them; in your hood, you should have space to place two. They go inbetween your current lights. They daisy chain off of each other through a small connection that they have.
So they require only one cord to power them up, which they give to you when you purchase them.
I daisy chained three of them and ran them for 6 months, I had the 11 inch series. You will have to see which one fits yours since your run 36 inch bulbs.
This light is intense and brings up the wattage of your tank allowing you to place Acros in your display. You can mix other corals in as well, I've stayed away from the blue corals that are intense light feeders.
My LFS only sold me what he thought would fair under PC lighting and you should do the same to be on the safe side.
If your theme is LPS, you can get everything you mentioned except the elegance coral, like Dragon and Incysor mentioned.
The key to keeping LPS or SPS healthy is not just the lighting, but the water changes. I use catalina water and I do a water change every sunday religously for both tanks. Each tank gets a fresh batch of 5 gallons of water.
I do not doze with anything, unless I miss one week; however I'm still seeing that it doesn't hurt to doze inbetween.
You also need some good water flow in a SPS tank and you can achieve that by placing a powerhead in the return chamber pointing outward if you are into concealing powerheads.
Skimmers are still very foreign to the nano cubes so I really don't have any input on them other than JBJ is going to launch one soon that will fit nicely without having to cut holes; so you might hold off.
Water changes are all you need for now, but I would love to have skimmer since I was a fan of one back in my reefing days.
Hope this helps you out a little.
P.S
I forgot to endorse the clams as a yes into your cube... I was flammed for being one of the first to push the envelope, but today they are just as vibrant as the day I got them, and growing too...
Mike