I did a bunch of research before I decided to build an AR. The CX4 has alot of features, but lacks quality high cap mags. As far as I know there aren't any factory 30 round mags, so you are limited to 15 + 20 rounders if you want to run OE mags. It would be a great weapon to complement a PX4 or 92FS, since it can use the same mags. You already know its limitations (range and kinetic energy).
Buds Guns had the CX4 .45ACP for $550. I just checked their site and the .45ACP and 9mm are both on sale, but you need to register to view the price now.