Those massive tanks are beautiful, yet may require a small mortgage. If you have it like that awesome, invite me over for dinner once it's set up, I wanna see too!
Personally, my obsessive nature is pushing me into larger tanks, so I'm siding with indoor ponds. Currently building a 550 Gal pond and at the same time drooling over a 6.5' x 10' @ 2.5' deep (almost 1200 US Gal) kiddy pool that will also fit in my basement.
Also I believe the fish will be happier in a pond like environment as opposed to a 24" thick aquarium. I think that, but no fish has ever really worded it like that to me, so there's room for error.
It's also worth noting that medium - large indoor ponds can be made to be astatically pleasing. My 550 will double as a coffee table (6'x6' @ 2.5" deep). If your not the handiest craftsman on earth but want one, I'm sure you could design it and hire a handy man to come build it for you. Mine will have about 6 hours of actual labor involved (although it is taking 3 2 hour sessions due to wood glue drying time)
Anyway, just throwing out options. Options are good to have!