Did the E package on mine and I am happy with it. Did not get a huge increase in accuracy. It does shoot 10ring at 25 yds, but it did that before I sent it in, just a little tighter now. Based on my experience, the difference between the pro-package and the E is the barrel bushing. I would probably just do the pro-package.
Good luck with your project. Please let us know your decision and results.
JW