Ok, thanks a lot guys.
So, the internal GK3-KIT BG it's only a way to hide the big body of the GK-3B, no difference related to the tracking latency.
In my setup, by already having an AWESOME SY-300 I'm sure that I'm looking more for a COSM synth stuff than a GR-55,because I already play synthesizers and the GR-55 synth sounds don't convince me at all,
I like the VB-99 and I could find one new here in Italy, but the only problem for me is that it is quite old, I read somewhere here in the forum that the technology inside the VG/VB-99 is obviously older compared to the GR-55 or the GP-10, also the VB-99 is very expensive almost 1300 € euro.
The best companion for my SY-300 would been the GP-10, but unfortunately for me it doesn't work with the GK-3B, I have to wait for the next NAMMs, it my only hope