"I read that some people have experienced poor stopping power from the Planet X calipers - worse stopping power than 105 calipers."
Maybe they do not know how to set up brakes. I ride down a lot of hills at pretty good speed and these work great for me. I would suspect that there is no difference from the forged and CNC brakes as far as performance. The Forged are pretty light as well. There seems to be a push that forged are just better but I have no reason to think mine are unsafe.
I can really relate to your wanting the best price on a part. I can honestly say I have not paid full price for any thing on my bike or the bike itself for that matter. Saving money and getting what you want is a wonderful thing.