I run a 14 gallon biocube and have had good success. Only really necessary modifications I made were to remove some of the wet-dry filter elements (bio-balls, sponge, grating) in the back chambers.
As for other recommended mods, replacing the stock filter with a maxi-jet 900 lowered the temperature and increased the flow, and that was a very simple modification.
I hear some Biocubes have the ballasts die pretty quickly due to supplier problems. I think I had heard the aquapods had leak problems. Definitely google around and get lots of opinions/information, because there could be problems with any of the brands depending on their suppliers.
Also, you might want to investigate nanotuners.com. They have upgrade kits as well as upgraded all in one systems, in case you'd like to increase the lights for keeping more demanding corals. I used one of their upgrade kits to add a third 24W PC bulb to my system and I didn't have too much trouble with it.