Floor standing speakers are a good and economical way to have more bass from budget speakers. The problem is that the best location in the room for the midrange speakers is often not the best one for bass.
As was already remarked, I have no idea what you mean by midrange slam. Anyway, I would first sit down and do some measuring. Personally my next move after that would be to see if some damping above the transition frequency may be beneficial. After that I would get serious about improving the sound around and below the transition/Schroeder frequency. The two common tools for that are multiple subs, or at least a second one, and dsp rooom equalization.
As was already remarked, I have no idea what you mean by midrange slam. Anyway, I would first sit down and do some measuring. Personally my next move after that would be to see if some damping above the transition frequency may be beneficial. After that I would get serious about improving the sound around and below the transition/Schroeder frequency. The two common tools for that are multiple subs, or at least a second one, and dsp rooom equalization.