I would move an RODI unit to the top of your list. They are not that expensive and will save you tons of headaches. If you want that full reef tank with lots of corals, this is the most essential piece of equipment you can buy.
Hannah hand helds: The phosphate and the alk are good, don't get the calcium one. It is all over the place and you won't get an accurate reading. I have not use the PH one so don't know about that. I have the calcium one and don't use it if you want to give it a try. When we use it against our salifert test kit, it just is not as accurate.
ATO: They are amazing and I love mine. I like the new pressure based ones as they have much less design to fail and they are actually either the same price or less than others. Another bonus is they look like they can connect to your controller if you buy it. I know Aquatic Obsessions carries them but if you want to take a look at one look here:
LEDs: Wait a bit and do some more research, new LEDs are popping up all the time with different color combos and price points. I am running the SOL blues right now and like them but don't love them. I am replacing them with Mazzara Ps when I upgrade. I think with the pending release of the vega the prices and used prices on them are going to come down as people upgrade. I think you are making the right move by getting rid of the MH, but this one you can take some time on.