its not power that kilsl box's its the torque.
i stripped my 3rd gear at 260bhp 280ftlb, might have been getting a bit long in the tooth, but i was giving it death on the isle of mann tt course
if you doing alot of track days then ppg gea***t might be the best option.
its not the power that will kill it on track, its the heavy handling, and the ocasional missed gear change will spit out the cogs no problem, so paying more now might be a saving in the long run.
as sugested your options are
recon the box - prob wont last
6 speed - dicks around with the ratios, still not gonna get change from best part of 2 grand but will be up to the job
5 or 6 speed ppg, straight or helical cut - def do the job and strong enough for what ever abuse you wanna give it, but will set you back best part of 3.5 for a the kit (2k) building, and uprated clutch plus fitting.
the sti box's are stronger than the uk box's, but not by much, as far as im aware the type r box's are just sti box's with dccd so wont be a big improvment.
all in all i think if your doing track days then you need to throw some dollar at it