Well, I just drilled a 1 1/2 inch hole and a 1 inch hole through the corner of my living room floor [corner tank] and dropped hose through to the basement ceiling. If you have that luxury, you can eliminate a lot of noise in your living area and confine the messy equipment [sump, skimmer, return pump, plus calcium reactor or kalk reactor] to a room you can shut the door on. If you can get plumbing in the sump room, even better---a drain to dispose of unwanted water---great convenience. If you want a midfloor system, and can build, you have several options: through the floor to a sump room; up above the tank plus below the tank [going with gravity helps]. I can tell you that a pump adequate to feed a 300g tank from the floor below is probably the largest Iwaki running full bore [put a cutoff in the line, just in case] and mounted [as Iwakis are] outside the sump, intaking through a bulkhead. The best way to describe the Iwaki sound is that of a small plane warming up. A door you can shut on that sound is a real boon.
My upstairs [living room] tank just gurgles quietly. Downstairs is much noisier.
A submerged pump, in the sump mounted underneath your tank stand, is going to be a bit more than a gurgle, [you also have fan noise from the light kit---mh bulbs, if you go mh, require fans to keep them cool]. So you will have gurgle and soft whirr of fans. Add the immediate racket of a freefall water entry [sump] and a pretty potent return pump, and you can see it can be noisy to have the sump with the tank. Now if you do a custom job, a little insulation in the stand could reduce that noise a bit. Mind, I had the whole business in my recent apartment, and it wasn't hard to share a room with. Just---a big tank requires a big pump, and a big sump has a lot of water moving. You have to consider noise and options.
Plus weekly water changes are easier to manage for a big tank [10% -or 30 gal] via a Rubbermaid tub in a sump room with a drain, vs trying to do the operation in the middle of your white-carpeted living room. It's real easy to combine, say, a laundry area with a sump room: both use drains, etc, and a concrete floor is a plus when dealing with lots of water. I have a floor drain, in addition to others, and it's a great comfort when I realize I may have left the ro/di water filter running just a little too long.
Did I mention autotopoff systems? A big tank may evaporate 3 gal of water a day, or more. My 30g sump has a float switch connected to a little maxijet pump in a 32g Rubbermaid trashcan full of ro/di-filtered water. It continually 'tops off' the sump to keep the salinity stable against all that evaporation [a gallon a day for me]. On its way to the tank it passes through a kalk reactor, which also delivers alkalinity and calcium support to the water system...a little convenience, reducing my need to put these things in manually. But another reason, especially for a center-floor tank, to want to have the works elsewhere. That tub isn't a thing of beauty.
Plan on about $25 per gallon, give or take a few dollars. Especially if you're not DIYing some things.
