If you are happy with your current riding position on your bike you should really try to find a new post with a similar setback to your current post. Find out the setback angle on the TCR3 post and work from there.

In regards to one and two bolt systems, I have used both and snapped both. From my own personal experience the one bolt system is a lot easier to manage, but the bolt can loosen over time causing the seat to slip back. The two bolt system is a little more fiddly but once you have it right I think it distributes the clamping force a little more evenly over the seat rails.

The post I am currently using is the thomson masterpiece and I have had no problems as yet.