The NX5 and NXA RS250's both use the same calipers and basically the same 296mm diameter discs.
The RS HRC manual will tell you not to mix certain pads with certain discs.

Click on the link below to get the parts manuals for both the NX5 and NXA RS250.

http://www.tsrworldwide.com/

Click on 'Parts List' to find the relevant parts.

An NXA front end will look very trick on your NSR!