The DSG map is worthwhile at any stage....even stock.
You'll not see any benefit from the extended rev range as stock, because the engine rev limiter will be set lower than 7,250rpm anyway, but you will see an advantage in how much smoother the car feels and the extra urge in the gearchanges. If anything I'd have even considered it before the Engine map. The two maps for the engine and DSG are totally separate and so you can have any engine map(APR, CC, REVO, GIAC) with the DSG map.
Again Statllers do this map for under £400.
I'm beginning to sound like a Statllers promotional vid