No idea what the FF boxes feel like, I put a rebuilt Police box (you could still get them back then) in mine about 10yrs ago. Still works great and was a definite improvement over the stock box that had started leaking.
Not sure what I would do today, but that's $150 you could use for something else.
As far as the over-assisted feel everyone talks about, I think I'd try this before spending $300 on a FF box.
