You have a valid point about MRX having no killer aps in the pipeline (At least not to my knowledge) but they do make acquisitions to further their dominance in their niche. As you point out, the potential for explosive growth is low but they do have the opportunity for steady growth with pretty good returns. That said, they also have a lower risk of crashing than the companies that are hung further out on a limb.
I wasn't familiar with CDHP but will look into it further. If it takes a dip I'll consider buying a small block.