Hi,
I have the Tyros 4 and I am very happy to have it, I upgraded from my Tyros 3 and is HUGE the difference.
In your case, depends on your needs, if for your work in the studio could use the beautiful S.A.2 Sounds, the new Drum kits that have been implemented in some styles, perhaps yes.
I think you should go an check that yourself, since you are the only one that knows you precise needs.
There is a difference in the Needs and Wants....
Just my 2 cents.

Manuel