The next thing you can do is replace the stock insoles with insulated insoles. Here in the U.S. we can get what are called Insolator insoles ($8), which are three-layer devices that include Thermolite and neoprene and that help prevent cold from coming through the bottom of your boot. Depending on how much room you have in your boots (keep in mind your feet will swell at high altitude), they may simply fit inside over your regular insoles.
Lastly, of course, are overboots. The very best, in my view, are Outdoor Research Brooks Ranger Overboots ($125). These are full overboots that completely enclose the boot. Gore-Tex uppers, foam insulation, very, very warm.
Take these preceding steps and your Salomon boots will be very warm indeed. But if your route guides advise you to prepare for extended bouts of sub-zero (F) weather, then plan on taking plastics.