I’m not here to give you advice, because I probably have a lot of the same questions, but here are a couple more things to keep in mind when looking at used hardtails.
– was it designed as a 29er, or is it a 26er frame that was modified to fit 29″ wheels when those became popular for XC? (I did some research on a used Salsa and decided to pass, because it was not their best effort… It was one of the earlier 29ers, and while it was built well, and had good components, the geometry wasn’t designed well for 29″ wheels)
– speaking of geometry, trends have changed in the last few years. The angles on a 2010 bike are going to be different than those on a 2017.
When you’re spending this much money, it’s natural to agonize over the decision, but the rider is the primary performance part on any bicycle. Phil Kmetz rode the shit out of a Tokul 3 and took it on a downhill run at a bike park.