The general consensus seems to be that AKP and Ivory are about evenly matched, each with its strengths and weaknesses. Largely a matter of personal preference.
At the current crossgrade sale price, AKP is a really good value obviously, and you will also be able to load its pianos into K2 (.1) for further tweaking.
I think either will be a clear step up quality wise to what you own...whether the investment is worthwhile depends on how important the piano is in your music.
If you are after the best piano sound, Ivory beats Akoustik hands down IMHO. I bought them both last year and haven't touched Akoustik since. If you want a piano that is more CPU efficient, then Akoustik is what you want. My only complaint with Ivory is that it is a HUGE power hog.
_______________________________________ "I would rather compose than decompose."
Quite a nice product although I had to spend some time optimizing velocity curves, harndess of the (virtual) keys and so on.
According to Synthogy, a fourth piano (a Fazioli) should be added to the Ivory collection "next week or so". You could give it a chance (if interested). I guess some Fazioli demo will be added to the existing mp3 demos of the Yamaha, Steinway and Bosendorfer.