I shot a Mag for years before I bought a mech Autococker. I couldn't get the hang of the trigger, and the timing was frustrating occasionally. I almost sold it, before my buddy recommended an Eblade. Solved the timing and the short-stroking. I love having an Autococker for the same reasons you stated. My suggestion would be to find an Eblade (or Autococker with one on it).
If you get an Eblade by itself, keep the mechanical frame and 3-way from the Rex M2. At times, I regret selling those off just for the times I want to tinker.
If you get an Autococker with an Eblade, you can decide whether to keep the Autococker w/ Eblade or put the Eblade on the Rex M2 and sell the other Autococker parts.
On PBReview, there's people talking of buying these for $80-$125 in 2006. Probably worth less today.
Last of the Salzburg Clan