OBVIOUSLY, as you've summized, a ReefKeeper or Apex would get your automation up and running faster, there's nothing wrong with that, it's what I did initially
The Apex actually has a better programming interface than the ReefKeeper in my mind but I still bought the ReefKeeper!
For basic control while you're building your own controller, you'll be able to save a whole lot of money by going with the RK-Lite packages (do you really need internet availability.. can be somewhat painful to implement)
An additional thing I did (My whole system was battery backed) - I put a 120V relay onto a separate plug outlet and fed the "Normally Open" contacts into a switch input... when house power was lost, an alarm condition was triggered, I turned off everything that was non-essential (lights / skimmer / return / excessive fans / dosing pumps) keeping flow running in the tank until power got restored.
If you post on any of the reef forums asking what is best, you're likely to get slammed with this is right, this is wrong - everyone has their own way of implementing their setup so take my input with a big grain of salt
Additional: If you do go ReefKeeper route, make sure you put the power bars and controller interfaces somewhere that doesn't get too much salt laden humidity.. those 6 way network type connectors they use are cheap and are susceptible to corrosion. It's easy enough to swap them out if they do corrode, forewarned is forearmed! I have no idea how susceptible the Apex etc is to corrosion as I don't own one