When I installed my 440 kit I put in a White Bros track cam, which is their race cam. The cam will help with quciker rpm's and your larger bore will help with the low end power. So I would say put the cam in at the same time. You will notice the diffence. As far as a difference between the Curtis Sparks and the Wed cam I could not tell you anything. From what I have read they both are good cams. Just be sure to put the spring kit in or you will float the valves.
2002 KTM 400 EXC, this bike is awsome!
Quads I use to own:
FDO 463ex, Gas Gas 300, Gas Gas 450, Rancher, Yamaha Warrior, ATC Big Red.
If you can't afford to fix it or replace it, don't ask to ride it!