Veloce and Saxo are very different.
If you are a trickster, the Saxo will be better. It's a smooth ride and
takes a beating. If you live in Minnesota like me, you go for more slalom
boards, like the Veloce. You can still trick and pound on it, but it will
have a little more speed and planing for cruising through lulls. It depends
on your application.
As far as ditching the older boards for the newer models, it's a definite
plus, and will improve your sailing. But if you are having fun on the old
rides, and don't want to cough up the dough for some new, or slightly used,
rides then don't upgrade yet. Fun is what matters.
For me, I won't buy a used board. Fins, no. Sails, yes. Booms, maybe. Masts,
only decent used carbon, never aluminum or epoxy. But used boards are
touchy. You never know what lurks beneath those seems that are about to blow
in a production board. Customs or epoxys can have a LOT of stress you can't
see until it's too late. If you sail an epoxy and it still feels stiff as a
4x4 (like it should), not like a soft production model, it's probably OK.
My two cents worth,