I know it's an odd arrangement for the sump to be above it, but it would still be out of sight with the stand I'm going to build... here's what it will basically look like... this tank belongs to a friend of mine and is SW, not Amazon, but you get the idea of what the stand will look like:

I guess the benefit to putting the sump above is that it would eliminate the possibility of flooding the way I want to do it... if the pump dies, it's no big deal, whereas if the pump dies on an under the cabinet sump, I could potentially have 150 gallons of water soaking through the floorboards. The sump will be approximately 10 gallons, but I will have to build it myself out of acrylic, or find a 5-10g acrylic tank for cheaper that I can drill the side on for the return line. The main reason for having the sump at all is to be able to hide all the equipment, heater, CO
2 injector, filters, RO water filler, etc., so that all I have in the main tank is the pump line, the return line, and the shutoff switch that will turn off the RO filter/filler when the main tank reaches it's full water level.
Underneath I'll keep a 10g quarantine tank... I'll just re-use one of my existing 10g tanks which I otherwise have no other real use for (I'm wanting to get rid of the 2 10g tanks, they are just too small for me now).
For substrate, since it's going to be a planted tank, I'm thinking of going with between 5-7 bags of eco-complete so it makes it a little bit darker than flourite (it's got a large footprint, but I think that much would provide a good base).
Things I definately want are going to be trumpet snails to turn the substrate, I would like 1 or 2 other larger above the substrate snails, but I'll have to see what I can get that won't eat through the plants. I'm not sure if freshwater clams would be true to the biotope, but I'm thinking about 5-10 of them. I think 1-3 plecos is a must (I already have 2 small ones, so I could just move them over to it). I've always wanted to keep a couple of tiger oscars, but didn't have room for them before, this. The problem is that I simply must have smaller schooling fish also. I wonder if a school of tetras could out-swim a single oscar to stay alive... I doubt it, but I wonder none the less. Also maybe a few cory cats, 5 or so.