See if you can catch a few, say a dozen or so sunfish. Photograph each one and then post them on here. We'll get an idea of what species you have. You may not need to stock any new sunfish, but rather just manage the ones that are already in the pond. I doubt any RES are present, so the addition of them would be a good thing. 5"+ RES would work. If you end up catch some of the sunfish and many of them are GSF, then the addition of BG would be prudent.
Can you get a photograph of this muckgrass? Determining exactly what it is really helps in determining how to manage it and if it is of value or detriment.
I think you can still stock CC, if you really want some catfish I see no problem in stocking some. With the bass population you have, I would recommend you find larger, say 10-12" CC to stock. If you feed the sunfish and trout, the CC will jump in as well and will definitely grow much better.
