well firstly, i love seeing tanks like this, full of oddballs instead of the usual suspects, and yes, get the biggest tank you can afford and can physically have in your house. over the years, my fiance and I have had many tanks scattered around the house, but i was more into my then tank, a 4ft one of mixed cichlids and oddballs, i then went and had a custom tank made, a 6x2.3x2.5 (not far off a 1000ltrs), even though it is a monster in the house because you also have to take into account the unit, which is alomst the same size, then on top of that, the hood, so when you have it all set up, you walk into the room and feel you walked into some aquatic place, it looks out of place, it looks too big but i wouldnt have it any other way, it is great! you just need to make sure if your floor can take the weight, my tank's footprints is over 1.1tonns, but i have solid floors.
it will also take a bit of time to get it up to your spec, decor wise, but once it is up and running, you will love it, so good luck in finding that monster tank!