In reply to zimpara:
The peaks mentioned have very different requirements and the insulated trousers mentioned are likely to be overkill for several of them. Normal softshell trousers with a base layer and overtrousers for the coldest / highest sections would be fine for many people on some of those peaks. If you are spending money on doing an 8,000 metre peak then buying or hiring down trousers for those will be the least of your money concerns.
Companies who guide these trips have their own recommendations and kit lists which are often worth looking at. You could always contact them for advice.
Have you looked at the ME Fitzroy trousers?