It mainly depends on your LS and Money...
Like me, my parents are paying the electricity bills... So have to go for a small size... And I wun be keeping big fishes... So 2ft cube is okay for me... lol..
You will see the power of the boxer in months to come... Trust me... I kept before... lol... Moult and grow very fast... It will attack with its claws if anythings comes near... lol..
It is the size that I am downgrading to... Quite decent if you have space constraint and not looking at a lot of fishes... 2ft cube is quite a big tank too... Just that the fishes will have lesser space to swim as it is not long...