Color Grading Tools to augment FCP X

I am looking for tools/plug-ins that can expand my color grading capabilities. I have been learning FCP X for the last 6 months or so. There are some very good tutorials (Michael Wohl, Color Grading Central) and I am pretty comfortable working in FCP X. But I feel limited in the techniques......OK, yes, probably me more than the tools. :)

For example, I am shooting bands in local clubs and the lighting is terrible. There is no way to add lighting in most of these small clubs (no room, no interest, owner liability, etc.). So, I end up with some musicians with bright lighting on one side of their faces and dark shadows on the other side. Some of this fits fine with the mood, but in other cases it just looks bad.

I have been struggling with color and shape masks in FCP X to deal with the bad cases, but it is really tedious. And the problem isn't just in a few frames, it last for the entire song sometimes.

This is just an example of where the FCP X tools seem to come up short for me.

I looked in detail at what it would take to use Resolve and it makes absolutely no sense for me.............I would spend tons of times learning complex capabilities designed for much more complex movies, and also spend a fortune on a separate computer system. Not an option for a hobby.

So, I am now looking at more powerful color grading tools/plug-ins in between FCP X and a full blown Resolve system.

What should I look at?