I cannot tell you based upon direct experience with the C-03xs as I've not heard that model.
Owning the C-02X and owning the C-03 and C-02 (and C1) in the past however, I can offer an opinion.
The likelihood of the C-03xs being a small or near-lateral move/upgrade seems to me to be quite high.
The C-02X, possessing alot of trickledown knowledge, design and components from the Grandioso C1 plus current advances
is a BIG upgrade from the C-02 I owned (still one of the best preamps I've ever heard back then). I am extremely impressed
with the C-02X. My suggestion would be to try and hear it, try to find a dealer demo of it and get warranty or simply negotiate
as much as possible as I did to a good price that works. You won't be sorry, even if you have to wait and put away more money
to do it.