Too many variables, lots of cars out there running almost 500bhp with standard boxes, the question is how long will it last if you drive it to it's potential, not long! You can easily do boxes at stage 3 level, but then again depends how many miles on the box already.
My advice would be don't expect it to be reliable at over stage 3 spec or running high boost on a stage 3, you cold have a 500bhp car and not launch it ever and it might never break, but what's the point if you can't use the power.? All for 4x4 by the way!
And without souding patronising, if you can't afford to get a decent box, you should't really have a car of that power as the other associated running costs could cripple you after a short while anyway.