Super excited for you - congrats on the big upgrade! I am sure you've thought through this (or at least your wife did - ha!) and know what you're getting into; however, a word of caution: reading through your journey I need to stress that bigger isn't going to be easier or less of a time commitment.
I'm sure you're excited today, but taking care of a tank that large - especially the first year to eighteen months - is going to be a huge time commitment. I mention this so that I can give you this recommendation: go in early on the APEX.
If you got bored with the first tank and started taking shortcuts, what has convinced you that a bigger reef tank will be different? Is it the additional opportunities for fish and corals? Great! That's the most demanding part of the tank journey (and not the cheapest, either).
You don't want to lose an investment in a large tank; the rule of thumb I've found to be true is that a two year cost of ownership is roughly $100 per gallon. So, my 300 gallon is a $30k tank... your 750 is going to be more, and how much more depends a lot the type of fish you get and on how much coral you buy versus frag. But the husbandry is expensive on it's own: every 10% water change you make is going to cost you $100. Heck, it's going to cost you $1000 just to put water in the tank the first time. A sump for a 750 is probably close to the size of most people's dream tank. Flow in your tank for corals ... you're looking at maybe $3 to $5 thousand.... and lighting a tank that large... oh the fun you'll have shopping!
All I'm saying is that you're going to be committing a huge investment into a tank that is amazing and in many ways also my dream tank (well, on the bottom end of a dream tank... I'm eyeing these new fiberglass 5000+ gallon containers with acrylic viewing windows measured in feet). But it's also a daily investment of time and patience - and if you've historically identified that you're quick to grow bored of the hobby... just reflect on that. Last Friday's BRS Live video actually addressed this in the industry: Ryan and Randy had a group of reefers that started the journey when they launched the YouTube channel and half of them were out of the hobby in 2 years. The other half are still in it. If you were given the opportunity to flip a coin and either keep $30k or give $30k away, you might not choose to flip the coin. Welcome to reefing.