If you have room and money for it, go as big as you can! I saved up for a while and bought a 110 gallon. My only regret is that I didn't save money just a little longer and get something bigger! You don't have to drill the tank or plumb in a sump, but you will want to make sure you have good water movement and no stagnant/ dead spots.
Look through the DIY threads and big aquarium sections, there is a wealth of knowledge on this site and people have setup large aquariums in a variety ways. Consider your goals and plants/ fish that you want to keep, and most likely someone has already setup a system that will work for you also.
Good luck, and go BIG!
