I have 2 FW community tanks, 4 fighter tanks, DP tank and am starting an aquascaped tank. We've just set up a 48G Marine tank but it's still cycling.
Go for it on the Marine tank, it'll be well worth it!
I used to have a marine tank and now have gone back to SW.
SW looks a lot nicer but takes quite a bit more time than a FW, i've only just begun to realise how much time my SW took to maintain compared to the new FW.