I have a 2006 Raleigh Mojave 8.0 That I have ridden all over the mountains of Utah. I want to upgrade my bike but i'm not ready to drop $3000 yet. Right now i'm considering just putting a new front shock on my bike and "upgrading" to the equivalent Deore components that it has, but they happen to be in 10 speed instead of 9. Will there be an issue with trading out the rear cassette with the new 10 speed?

I've debated back and forth on the benefits of having a full suspension bike vs hard tail, and I haven't really let my bike stop me from going anywhere so i'm looking for the cheap upgrade on my current hard tail.