Paragon can be a pain in the ass for gear other than skis and boots because that part of the store is staffed poorly and gets crowded. If you're looking for a lot of room to try on stuff with your helmet you won't have it. But I think they have a pretty good selection.
As for Killington, there are a ton of ski shops on the Access Road, as Max Capacity pointed out. Personally, I like Northern Ski Works, and I think they have a decent selection of high-end goggles, helmets, etc. But any number of places up there should do. Good luck.