having completed kili (09), elbrus (10), and attempting aconcagua (dec 2011), the thought of potentially doing denali is beginning to creep into my mind. my question is how much training/prep is realistically needed to do the west butt route. rmi, img, and alpine ascents websites all seem to suggest that prior experience on rainier (or another training course in the U.S.) is a requirement to join their expeditions. a couple others are saying that it's not necessary...so i wanted to get a few unbiased opinions.
given that i have done some glacier travelling from elbrus and have experience with crampons, ice axes and self arrest...is it unreasonable to learn the rest of the stuff on denali (ie, crevasse rescue, use of ropes, etc.)?
also, with all of the end-of-season clearances, i'm looking to pickup a down parka. there seems to be mixed opinions based on the message boards and the few guide companies i've emailed - but is the Mountain Hardware Sub Zero SL parka sufficient? Or do I really need the Absolute Zero?