Hey honda200exr;
I know I am a little late, but I felt the need to jump into the fray, only because I talked with Mike at Custom Axis about the same question. I ride XC and currently have TCS on my 400ex also. They are nice and I believe you will love them, now I realize that the rear needs some work.

Mike said that triple rates are much better for mx and the TCS dual spring has too light of spring for XC. You can tell because when you sit on the quad, the silver spring compresses and you are then relying on one spring (which I think TCS is trying to achieve). However, it is still riding on one main spring pretty much all the time. He explained, that there can be a much better combination with a stiffer small spring, so normal bumps are absorbed by the medium spring and the hard hits are taken up by the main spring. Custom axis dual rates have different spring rates that use what I just said. I have a set of PEP triples and they do feel alittle better because of the medium spring.

Too little too late, I know. You will still love them, just thought I would pass on what Custom Axis had to say.

Nick