you can't just unbolt the knuckles and swap the GSR knuckles on unless you swap the hubs. The STD axles are smaller and splined differently than the GSR axles, and the GSR knuckles are taller.
What you CAN do, however, is put the calipers, caliper brackets, and rotors from the GSR onto the DX hubs/knuckles, and it should work fine.