Re: Hacking my way through hyperbole
150 yd will probably be enough. If a fish has already pulled that much off your spool he will at least be somewhat tired and will be more likely to turn rather than keep going in the same direction hard enough to break your leader. (If not, better hope it's the leader that breaks and not a soft spot in the backing, though.)
On the other hand, you'll need another reel to go along with that new Axiom anyway, so as long as you're getting one you might as well get one that holds 200 yd or more, just to be on the safe side.