Novation MKS 61

I use a novation MKS 61 connected to an open labs SoundSlate. Unfortunately, I am not able to get a good sound from any of the pianoteq pianos. I have searched the forums for ideas but still no luck with the sound.  I run the signal in stereo and have used different mike positions.  What I am hearing are very harsh tones throughout the low mid and high frequency range.  Do you think upgrading to the pro version will help??  Or any suggestions will be greatly appreciated.  I do use other piano VSTs with great results like Real Piano and pianos from native instruments. I am not ready to give up on pianoteq yet.  Thanks