Caspian has a geographical vibe, unfortunately an unhappy one because the sea is so polluted and starved of fresh inflowing water that it is an environmental hazard. Steps are being taken, it seems, but they'll have to be good. Cas doesn't appeal much as a nn, and I'm afraid that, rather than Ian, the go-to nn for Caspian would sound more like Peein'.
I would have named my son Ian in a heartbeat, but at that time it was impossible for family reasons. I still regret not having an Ian son: my two closest guy friends are both Ian, and I've never known an unsatisfactory one.