Well, youre correct in that they arent cheap, they seem to give alot more nice cold air into the engine (the top of the engine/inlet manifold is still really cold even after a good run), remapping was required to actually get WOT to be a correct air/fuel mixture across the rev range (as you might expect).
As for noise, well, its hard for me to hear cos I have the K-tec (feck loud) exhaust, so no real chance to hear it much hehe.
If you search through previous posts of mine you can see the power increase gained from the remap after I had the kit fitted, but unfortunately I didnt get a standard setup power run before I started modding.