I know this post is ogling to be purely subjective but I always welcome tons of input so here goes:
What would you recommend of the products below?
Controller: Apex or Profilux? (traditionally used Apex in the past)
Lights: Radion or Mitras? (ran Radion in the past)
Skimmer: ?
Return pump: Cor or Vectra?
Tester: Tritan/ION Director/KHG? (had KHG testing ALK and going in the past)
Salt: ?
Sand: ?
Looks like this will be a fun one! I have some input here since I just set up my tank using a lot of the equipment in question here.
I only have experience with APEX, so I can't really do a comparison, but I know that Reef Automation (Derek Picker) does a great breakdown between the two on his YouTube channel.
I don't think you can go wrong with either... I love Ecotech and the customer service you get with them.
I personally feel like Reef Octopus is one of the most reasonable high-end skimmers out there. I have the Regal 250INT, but Elite has some other features that may be important to you.
I actually have both the Cor and Vectra running on my tank. Having said that, I haven't been running them long enough to give you much insight other than I like them both. If you end up using the APEX, there are some features you can get with the COR that you can't with the Vectra, but for me, the battery back-up capability of the Vectra makes that my choice (unless you want to do a DIY battery back-up for your COR).
You tester will likely depend on who you go with as your Controller, and I haven't even hooked up my Trident yet, so others will have more insight than I do on this.
For salt, I use Brightwell for a number of reasons (availability, decent Alk/Ca/Mg numbers, clean mix, etc.), but I know others swear by other salts. For me, it comes down to a reasonable price, availability, and numbers close to what I'm trying to keep.
I personally have to have sand in my tank... I went with a mix (some crushed coral for the high flow parts, then mostly CaribSea Special Grade and Reefflakes for the rest of the tank).
Good luck!