Thanks everyone, I really appreciate the responses. I can see both sides of the argument, and from here it really seems like it's a personal decision for everyone based on a number of factors. I sort of expected that, but it's still nice to hear why people made the decisions they did.
I'm an engineer (please don't hold it against me

) and a bit of a gearhead, so I'm really enjoying the planning process and love the idea of putting together a large system with automation features. We just bought a home with a family room and an empty section of wall that's screaming for a tank. I've toyed with the idea of running the sump out of my workshop in the basement along with an ATO and AWC system. I haven't worked out all of the details but I've thought it through enough that I'm fairly certain it's feasible. My GF also has a wholesale account with a pet supply distributor, so I'm able to save a decent amount of money on equipment costs.
That being said, that is obviously a HUGE investment into something with which I have no practical experience aside from freshwater and cichlid tanks (and 20 years of dreaming about it). So, I think, right now anyway (I've been going back and forth for days) that I'm going to go with something relatively smaller, sort of a "proof-of-commitment" before I start making alterations to the house. I figure I can still set up a RODI and ATO+AWC station for the smaller system using larger components that could support a larger system.
If after a year I'm still committed to go huge, I can start doing so, and if in the off-chance I drop out of reef husbandry, well, at least I don't have to patch any holes in my floor.