The slot blocker is well worth the money.
Keep a few Q tips handy. I find the pump stroke degrades quickly if you get dirt or paint in the holes that the pump rods run through (side of the body).
A tech-T bolt is worth considering. It will raise your velocity by 20-25 FPS. It has O-rings with the stock bolt does not. The down side is the front o-ring rubs against the detent making a rub/click when you close the bolt.
The quad rod kit is a big upgrade from the stock handle ($70 contact CCM Chick). It takes the last bit of slop out of the pump stroke.
Have fun, get used to being awesome.