A few more questions to ask yourself:
On the Evo are you thinking the 650 or 29er version?
What kind of riding are you doing and where? I've ridden at LBL and know the conditions there and am not that far from you in the scheme of things.
If you start new, do you really want to stay with a hardtail or make the move to a full suspension like the Camber?
I'm one to ride a bike for a long long time before I can justify starting over (I'm still riding my '09 Stumpjumper Comp 29er hardtail) but I think you may be at the point you want to start with something new instead of patching up something that old.
Just my two cents, start new and go 29er. If you were bombing down all mountain/downhill stuff out west I'd say 650 but for most of our Midwest trail types/conditions the big wheels are an outstanding way to go. I made the jump back in '09 from 26 inch wheels and was warned about 29ers not being any good on tight trails, etc. but honestly could never really tell that big a difference. And the benefits of the big wheels rolling up and over stuff easier were pretty noticeable. If your local bike shop has loaners I would try to get out and ride a couple of different wheel sizes/models.
Good luck