The first question is what you find lacking in the Audya. I have an Audya76 and SD40 and Sd2 modules, as well as Pa4X,Yamaha S970, and Hammond SK1 keyboards. The Audya tops them all in live sound. The Pa4x is my next favorite all around board due to easy navigation and easy editing, as well as great VH, reading midi lead notation and lyrics, and numerous other modern features.
In other words, if your decision is based on features not found on your Audya, and not sound quality, I would vote for Korg Pa4X. If it is sound and styles, I would keep my Audya.
pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact