If indeed the stage is that rare to get on sale, then why not try it out--resale should be a breeze? Note that it won't work with your present cart, since the gain is too high. But if you want to play at this level, you'll want to get a better cart anyways, so put that in the budget.
So, to answer your first question: yes, it would be overkill.
So, to answer your first question: yes, it would be overkill.