I had a 5x2x2' tank in my bedroom with a sump and an open 4x2 stand, you very quickly get used to the noise. It was lucky I could hear it, because one night I woke up around 2am it sounded really strange. The water would stop flowing for around 20 seconds then go WOOOSHH!! like someone flushing hte toilet. After listening to it for a few minutes trying to figure out what was happening, I got up and turned on the light to find my 14" fire eel in the overflow trying to swim down the pipe to the sump, but he was too fat! His head would block the hole while the water would build up, then he'd give up and pull out and all the water would go rushing down.
Aaaaaany way....
I'd say a big sump set-up would be fine. You don't need a canister as well, and its just another big expense. [it won't hurt to have one tho, but they're not necessary] Get the sump custom made by who ever is doing the tank (the mught do you a deal) and make it so it will fit nicely under the stand and so it has a big tower for the media above and below the water. You could convert an old tank, but you'll probably end up with something that doesnt make good use of the available room under the tank.
Two FX5's might be easier to set up, but they'll be much more expensive [so not really easier if you consider the amount of work you'll have to do to get the money to buy them!], and no where near as easy to clean and maintain as a large sump.
You've got plenty of choices for fish. You could go with a random assortment of monsters like the big tank at HFF Albany (aro, dats, cichlids, clown/royal knife, large barbs etc), or something with more of a theme like a large central american cichlid community.