I've got a 54 corner as well and I think it's great. I have the same problem with space so it fits perfect in my living room. It's totally true about the aquascaping and space under the tank but it is impressive to view. Only thing I regret with mine is that I didn't get a corner overflow so It's definitly one thing to consider because certain tanks..mine included...can't be drilled. As far as a sump goes I just had Bow Valley build me a custom 18 gallon sump. The other problem is canopies...If you want to upgrade to a canopy that sits on the tank you'll probably have to get creative with wood to make it fit right.
