If it's just the hub cap that needs changing then I wouldn't bother. Save yourself 40EUR.
When my Raven Nomad was being spec'd Thorn asked me whether I wanted a DB version even though I wasn't planning on using disc brakes. Their argument was that it would offer me the flexibility in the future. (In the end I declined because I'm never going to use disc brakes on this Nomad, but I could see their point).
Not sure about resale prices, somebody else will have to answer that. I can see the advantage of having a new one for the warranty, though.
Shaun