DT240’s aren’t silent, but are quieter than Hope’s…
They’re reasonably quiet, though the volume does vary in a slightly erratic and possibly annoying way- it’s basically a DT240S
It’s odd, but I’ve got 2 sets of 240 hubbed wheels right now, and I’ve owned another set of 240 hubs and a set of 440’s too before… NONE of them have been the same volume! One of my current rear hubs is almost as loud as a Hope (annoying, and I’m gonna try and quieten it), the other is almost totally silent… How strange! 😕
GREAT hubs though… Highly recommended, best ratchet design out there, and so simple to strip and service.
As for carbon rims? Your money, your choice, personally I think there’s no point whatsoever on a Mountain Bike, even if you’ve got the money to spend on them… Too little return, for too much outlay, when good ally rims are a fraction of the price.