All intakes will make your car louder.
However, the conforti intake is the quietest intake of all intakes due to the ITG filter. ITG filters better and breathes better as well, especially when dirty. I've used both, currently using a K&N because that's all that fits in the GruppeM. Otherwise I'd have an ITG filter in there somehow.
As for warranty. Yes and no. It will void the warranty on your MAF from the get go perhaps, but that's about it. If any damage occurs, the dealership needs to prove the intake caused the problem. ANd if something does happen, they will indeed blame it on your intake. However, out of all of these "horror" stories, the dealership hasn't won once. The stories all ended up with the manager bending over and taking it up the butt and apologizing for the stupidity of the service advisor and techie. For example, the worst story i've seen was the dealership blaming the intake for a dead battery..
uhhhh. yeaa.. you can guess one won that one...
anyway, even a dinan intake will void your factory bmw warranty. That's the key phrase, factory bmw warrnty. Using dinan parts replaces your original warranty with a dinan warranty. THe bad thing about that is, even if it is an authorized dinan dealer, a lot of them won't honor the warranty for some strange reason and will send you somewhere else.. i guess an authorized dinan warranty place..?!?!?
I suggest going with your original plan, the conforti, or the benfer if your prefer dinan style..
hope that helps..