@stanleo I think an Apex is a "nice to have" not a "must have". I'm a newbie reefer with a 120G for about the past 18 months. After a lot of thought and comparing it to GHL, I picked up an Apex in December. Here are a few of my thoughts.
1. It's nice to have the Apex as a backup / safety monitor. For example, my heater is using a separate controller, but if my tank temp goes too high or too low the Apex shuts off power to the heater and sends me an alert. I also have two moisture sensors that send me an alert if they detect water (which likely means a leak) and also then shuts down pumps and stuff.
2. It makes some things more convenient. I set up a few buttons so that when I want to do maintenance, I flip a switch and it turns off pumps, heater, etc. I also have an "Emergency" button that basically turns everything off as well.
3. No plans to connect it to a Trident, so I'm pretty much using my Apex for monitoring and limited control. But I still do manual water tests twice a week, etc.
4. For your gear you don't need to replace any of it. It's more about how much control can you get from your Apex. I really only use it to turn things on / off. I have a Vectra M2, two MP40s, and a Versa doser that all run off Mobius.
5. If you're planning a long vacation, you might be better off with a trusted "tank sitter". To fully automate everything that you might need (auto feed, ATO, auto water change, etc) might take a while and then you need to grow comfortable that it's working as expected.
One last thought -- having used the Apex for a few months it's definitely nice to have, and it makes some things easier. I know some people have "fully automated" their tanks but I'm not one of them. Also, knowing what I know now -- GHL might have been a better choice.
Good luck with your decision!