Hi Texas and

to TR!
I have both a 54 gallon corner and a NanoCube 24. It is an advantage to have the extra 50% water volume, especially for a first marine tank, but as Scott mentioned if you have ever treated it with
copper you may have trouble getting the
copper out of the seals.
Have you considered buying a used salt water set up? They are often available on aquarium club boards or craigslist. This would be a way to leverage your initial purchase funds into more and better equipment. I got a great deal on my 54, I paid $200 used for the tank,
sump, return pump,
skimmer, chiller and other misc equipment. This was probably $1500 -2000 worth of equipment. Even saving tons of money by buying used equipment this is not a cheap hobby. I have easily spent another $1000 on
LR, sand, equipment, corals and fish. And, that doesn't include my Solaris light.
Many reefkeepers don't use a filtration system in the same sense that fresh water tanks are filtered. The
LR and LS is our filtration system and we may add a
skimmer. I have a
skimmer on my big tank but not on my nano. A filtration system that uses bio balls is not good for marine tanks if you want to keep corals.