If all your racing is against the 400ex, it won't even be a race. My buddy has a 400 and I can literally ride a wheelie while outrunning him. The moe modern 400s are slightly closer. The. 450s are pretty quick but the ones I ride with top out while I am shifting into 5. Never been around a 700 raptor or kfx700. Only thing I have lost to and I was stock was a built zuk 450(built 525 kit) and he left me until bout 1/2 way through 4th, caught and passed him then hit 5th. I do not know what these guys have done as far as gearing, the zuk was geared down and on 18s for mx.