I'd like to add to the above. You seem to be on the right track. Research first, then make a decision. I can also tell you that, as long as you are willing to keep regular with the maintenance, a saltwater tank is much more rewarding than FW. The first thing you need to do is to figure out exactly what you want. Fish-Only? Fish-Only with Live Rock (fowlr)? Reef tank? and if reef, what type of corals? These decisions will affect some of your equipment needs. If I were to make a few suggestions:
Go with the largest tank you can afford, and have room for. If you have room for a 125 gallon, and can afford it, go with the 125 Reef Ready.
It's not required, and many folks effectively keep reef systems without them, but I HIGHLY recommend use of a sump.
If you plan to do a Fish_Only set-up, Plan for future reef upgrade.
Most importantly, Regardless of the decisions you make, allow plenty of time for preemptive research. The more you know before you start, the better equipped you will be to make the right decisions, and the better your chances are for prolonged success.