Could we have your name?  Most of us know each other's name and we flip back and forth from real names to these goofy RC names on these discussions....otherwise I will just nickname you "Tiger"
I moved back up here from Florida after 18 years and my last tank was a heavily planted Discus tank.  I still have not seen any nicer Discus than the ones from Jack Watley (he personally collected his strain in Columbia, Brazil and Peru) in Miami....they were incredible.  I had the undergravel heater, Co2 and the works.....I too had been in freshwater for over 20 years.
Anyway, after my tank sat empty for several months my wife asked why I had never tried a saltwater tank.  Well, the first reason was I knew nothing about keeping a saltwater tank.  Now I know the first reason should have been the cost factor....lol  
If you have a money tree in your backyard and money is not a concern, then rock on.....but I would suggest you make sure you know what all you need for that 75 to do it right before going too fast.  I would play around with the 30 and see how you progress.  Some things you need to consider....do you have a RIO to make your tank water (if you are taking it from your sink it will catch up with you), a GOOD skimmer ($$), enough live rock (1 to 1.5 pounds per gallon), the right kind of lights ($$$) for the corals you want to keep, etc, etc.  There are a lot of knowledgible reefers here that can provide you with the knowledge to make sound decisions and to improve the changes of a successful transition...not having the right or quality equipment can decrease your chances of long term success....
Okay, some wiseacres will say I am scaring you, but I am a realist and want you to succeed.  You are right where I was about two years ago....and I am having a great time....
Kerry
P. S. - Stay away from a guy named Jabo, he is creepy!  Word on the street is he is not coming to the meeting on Sunday, so attendance should be good.....