Yeah, the Atlas Pro is basically a ready-to-go version. It's about $500 more expensive, whereas the belt mod itself is $200. If you have mechanical skill, I would say get the original Atlas and the belt mod, save the $300. If not, the Atlas Pro is a good mount.
I'm also not really trying to discourage, just make sure you know exactly what's involved. If you are up for it, it's an awesome hobby, and it is most definitely rewarding.