Discussion about the Korg PolySix synthesizer

Hello all, I have been working with a P6 that seems to be in good 
shape however it seems to be lacking in sound quality and dimension. I 
really am not a synth player so I'm not sure how to get the best 
results with all of the pots. I have loaded many different patches but 
the results don't seem to match the glowing reviews. 
I have watched all the youtube vids but I can't tell what they are 
doing with the controls to get the richness and depth or if they are 
using the factory patches and such. I ran it thru a really good tube 
amp and all the crazy warped sounds were pretty impressive but I can't  
get the basic voices to mimic what they are meant to (some seem close 
though).
The unit is very clean and the battery has not done any damage (same 
shape as the original batt but has a white cover).
Anyway I would like to put this up for sale but I don't want to 
mislead anyone about it's functionality.
What would a calibration do for it? Any ideas.
Thanks for any input you can spare.