I couldn't disagree more with your statement. You're only serious if you have space and money for a larger tank?? Anyone with a smaller tank isn't actually serious? C'mon man, give me a breakA 6ft long 150-180 would be minimum if you are serious about hobby.
The tank itself will be the least of your expenses anyway imo.
If you don't have room for 6ft they make some pretty nifty 4ft cubes that hold a descent amount of water.