I'll do you one simpler for less than $50 and smaller.
This is the 30A version but there are so many models of different sizes. I can also send you pictures of how to wire it all up if you'd like.
So that unit will provide 8A/channel according to the specs. You will need to work out the power per metre of the LED strip you're using and multiply that by the length that would be connected, bearing in mind you can cut the strips down. You might be able to run 2 x 5m strips off one controller, but check first (some tape has greater density of LEDs so uses more power).
You might be able to use one controller for the whole lot if they're only short runs, but you will have to buy and then run extender cables to connect it and you might have a simpler time just getting, as you said, one for side of the stage. This will also give you the ability to have separate colours each side.
Additional equipment:
You will also require a 12V power supply for each controller you have, something like this. So that would likely be one each side of the stage. The output power should be suitably rated to provide as much as the total amount of power you will use in your strips. If the controller provides max 8A/ch then that power supply I linked will be adequate, however you will still have a maximum length you can connect to a single controller.
The math:
If your strips are, for example, "maximum 12W/m" that is 12W over 12V which equals 1A per metre of power draw at full white, would be 0.33A per channel per metre. So you could connect up to 24m of this example strip with that controller (I wouldn't push it to the max though, some spare headroom is nice when dealing with cheap electronics like this).
It was the PSU! I replaced it with this one and now I'm printing again!