Thanks for all the advice. Really all I was going to do is put an XT rd on my Sirrus and put the LX rd that was on it on my Trek. I wasn't planning on turning my Trek into a 9. I don't do real technical off road stuff so the 8 speed is fine.
I am really not having any problem with either one of them other than some chain slap on the trek.
Do you think the LX would help with the chain slap? I have heard the LX spring is quite a bit stronger than the Alivio.
Thanks...