Well they state 235ps, its what Andrews (DTUK proprietor) Octavia vRS TDI made on a set of dynos once they had completed the map development. Dyno accuracy could be discussed all night though couldnt it.
I think with their stage 2 box you'd be looking comfortably in the 210/220ps mark real world.....still a healthy gain.
Interestingly ABT make a tuning box for the Mk7 GTD (and I am sure other 184 TDI variants).....they state 210ps and 317lb/ft torque for their box.....more interesting still they sugges the official figures are 0-100 7.3 secs and 145mph top speed.....so off the mark and top end v little quicker than the stock car....id wager the extra power just provides stronger mid range muscle...less gear changing etc.
To the OP, no the standard 312mm front/272 solid rears will cope just fine with the extra power....the GTI with 220ps and no PP has exactly the same anchors just painted red....and they can cope with 300ish ps for road use (sort of power GTI makes after a map)