Hi Buranda,
Going back to your questions. 4 out of my 6 fish tanks are small tanks, so maybe I can post some suggestions? I hope I will not set your head spinning as there are as multiple combinations / options as any imagination can bring. Fluval Edge. I agree with Jesnon – it is created to be “trendy” – and there is nothing wrong with it. The Edges do look superb, indeed. However, what Jesnon said is correct – they have a “fiddly” entrance for maintenance and also have limited options on live plants. A while ago, when Jesnon was creating her set up, I posed a link for her with George Farmer (a very famous “aquarium plants person”) planting an Edge – for the sake of me, I cannot remember now what was the name of the thread... maybe Jesnon can remember?
Colin’s suggestion is good as well – plenty of media can be put there so it is a definite advantage. However, that LPH question (sorry, Colin!) and the fact that the output of the filter – I believe – is fixed and cannot be adjusted may pose a little bit of problem if you intend to put live plants in...
Most of my relatively small tanks have external filters – I find it very convenient, easy to maintain, aesthetically pleasing (no bulky internal filters inside) and certainly very well “overfiltered” and flexible – you can play with positioning of inflow and outflow. Mind you, all my tanks are “open top” – e.g. there are no hoods which I dislike and this also allows greater flexibility of arranging things. I do have covers – custom made glass ones with the cuts for equipment. I know this is a more expensive option but apart from your space, it also depends on your budget.
Maybe it would be a good idea just take one day and travel around aquatic shops in the area close to you, seeing what they have on offer? There might be something which you never saw before but rather like... Possibilities are endless....