Thinking of upgrading to full suspension. My trek 3900 has been great but rides are killing my back. I am on a budget around 1K. My bke shop deals giant trek and specialized. i was looking at the pistol 1 from giant and the fuel 70. i am waiting for my size frame in oth to sip to my LBS for a trial ride. any opinions on these, i have read the few reviews in this website. any input would be appreicated.