Well, to some extent, you need to ascribe to the Big Pot Theory of gear-buying. It’s based on the notion that if you can purchase only one pot for the kitchen, then you really should buy the biggest one you are apt to need. In which case, a ten-quart stockpot may get occasional use heating up a can of Campbell’s. Similarly, when purchasing cold-weather gear, it’s perhaps prudent to buy gear that can withstand the coldest temperatures you are apt to confront. For Denali, that means temps of minus 30, depending on whether you climb in May or June. Low temps on Aconcagua are similar. Factor in wind and the debilitating effects of high altitude, and you’re looking at pretty damned cold conditions. We had pretty balmy conditions when I was on Denali six years ago, but I was cold in my minus-30 bag at the 17,000-foot camp. I carried a Rock & Ice on that trip, Feathered Friends’ premium down parka (around $600, depending on shell), and it was worth every nickel.
That said, you probably can get by with a bit less in some areas. Feathered Friends’ Icefall (around $400; www.featheredfriends.com) is designed for expedition use, meaning it could handle Denali and Aconcagua. I’d agree that you’d get more all-around use from this piece, although it’s still too warm for just about anything in the United States aside from winter climbing and camping in places such as Wyoming. I think you’d do fine with this piece.
Really, same for the Widgeon ($500). Although it’s rated to minus ten degrees, Feathered Friends is typically pretty conservative in its ratings. You could wear the Icefall to bed on cold nights, along with some heavy fleece pants, and be warm enough. You can also add a vapor barrier liner ($25) to the bag, adding maybe five or ten degrees to the low end. Also, carrying an extra sleeping pad聴a self-inflating pad plus a light, closed-cell foam pad such as a Cascade Designs Z-Rest ($36; www.cascadedesigns.com)聴will really help you stay warmer at night. You may still have a few chilly nights, but you’re unlikely to freeze to death.
Good luck with your climbs! Big mountains, both.