In reply to HosteDenis:
> ... I do get cold feet rather fast. Allthough I guess the Spantiks should suffice.
I've only used Spantiks to 7134m, in the Pamir. I don't normally get cold feet (though in Antarctica I always used Olympus Mons) and at about 6700m on Peak Lenin at 5am I had a very cold foot. The Pamir is colder than the Karakoram, and the Karakoram can be very hot even at 6000m, but at 7500m most mountains are pretty cold, particularly on summit morning.
Personally I think 7500m, or lower, is the upper limit for Spantiks *for most people* - I know that some people have used them climbing new routes on 8000m peaks, but you are not those people
I love La Sportiva, but they have been known to write some complete rubbish about their mountain boots in their marketing material (Baturas on Everest etc).
Karakoram moraines will destroy Olympus Mons or simlar soft altitude boots, so take a lighter single boot for low down and use the OlyMons higher up. If you know you get cold feet easily, Spantiks might not be warm enough for you above 7000m. Clearly Spantiks are better for technical climbing than Olympus Mons, but if you're asking this question and have not climbed in this way before, then I'm not sure how technical your route will be.