Given the list that you have provided, I would go with the Bits o' Mayhem. Since you already have the other two (I am assuming such from your statement about completing the set) having all the little bits and piece like the flaming cars, barrels, et al of the BOM set you might find greater usage out of that set.
The harbourmaster is a greate little display piece (for me that is) and could work as a mansion in a modern setting (or as you say a haunted house) but it's usage is fairly limited in your description.
The new set looks great and it looks as if you will get a great deal of flexibility out of it, but since it has just been released, there is a slight risk of it needing a patch so I would wait a little while to make sure all the kinks are discovered from it.
Of course you could always just but all three set now, couldn't you
