Removing the filters and not shooting so wide open has already made a huge difference. I guess I have read so many negative reviews since I got the camera that I thought perhaps it was its performance.
We have seen SO many people on here.. with filters, shooting wide open, shooting handheld at low shutter speeds, etc.. ALL getting low IQ, and they were ALL convinced it was the camera or the lens! lol! Glad to hear that helped! Post some shots....
One thing that you may also consider is fine tuning your lens. In your camera settings is an option called "AF fine tune" and allows you to adjust the focal distance slightly closer or further to make sure what you focus on is what the camera focuses on (if images are soft or focus is too far/close for where you were shooting). This helps illustrate what I mean.