hope we didnt put you off from keeping puffers. you can certainly get a GSP to take from fresh to marine. they are definitely just as personable, if not more, than other puffs. i had one and really enjoyed him. i will get another one day. get your "feet wet" with a GSP, ceylon or some similar small-ish puffer you wont regret it 
I'm glad you're making the responsible decision to wait. Be sure to stop back in here when you're ready. Or stick around & learn--we have forums here for non-puffers too!