I guess I'm alone in my perspective here. I view ADA style aquariums as art. Although I've seen better layouts then Amanos tanks, I believe his over all appearance of the aquarium it self it beautiful artwork. The the low iron rimless glass, the simplistic stands, the hand blown Co2 glassware, to the naturalistic landscapes, and the modern hanging lighting systems. It's all part of a "look" that separates his aquariums from anyone else (that I have seen). Hanging an overflow box or drilling holes in a $4000.00 aquarium is not an option.
One Fluval G6 can handle an aquarium up to 160 gallons. I have two of these on a "155 gallon". So biologically, chemically, and mechanically I'm more then set. I understand that flow is important as well and if I do need it then Vortechs it is. ADA sells a little surface skimmer which I might try first.
As far as a layout is concerned I'm not sold on any style yet. The current Unzan stone video thats floating around looks appealing to me. I don't want to paint the tank nor do I want to put a background on it so Hiding the back wall with a mountain like seen seems like a good idea.
I agree that ADA makes attractive equipment and aquariums. I've ran 60P, 90P, and 120H setups, down to ADA filters, CO2, lighting, etc. And I'm all for aesthetics being an artist by profession. But having seen both an ADA 180P and custom tanks, the silicone work is pretty even once you go over that 100 gallon barrier. They share the same nicely polished/beveled edges, and clear Starphire glass. Something to keep in mind is the seams on the big ADA tanks aren't nearly as invisible as their smaller tanks.
This is pure personal preference, but a single low profile overflow is less intrusive than 4 hoses and connected equipment. (Anything hanging on a rimless tank breaks the ultra clean look.) And if you haven't used glass pipes before, they are amazing fast at attracting gunk. They're also tricky to adjust for circulation/aeration given how quickly the water level fluctuates. The intake pipes have killed plenty of fish/shrimp as well, those minimal openings have surprisingly strong suction with a strong canister filter behind them..
I also used a Fluval G6 and can say that rating is more telling of the biological filtration capabilities, not the flow. I had it on a 46 gallon tank, worked perfect for that application. Like you said, nothing a vortech can't fix if you need more flow.