In reply to ThereAndBack: An 8000m peak may not be much colder temperature wise, but you will feel colder as you are likely to be much more hypoxic at 8000m instead of 6000m. Obviously it changes a lot from day to day, it might be -40 on denali and -20 on say, Shishapangma. To that end I would just recommend getting the warmest one you can, which will cover both bases. Denali is pretty cold, I would say similar to Cho and Everest, but like i said you may need warmer mitts etc really high as you'll be suffering a lot more.
Also, if you get a really good jacket, then you'll only need to buy down salopettes when it comes to the high peaks, instead of shelling out for a one piece suit.
Hope that helps.