Definately enough power for elk. The info I have seen suggests that powerbelts do better when they are not pushed to 150 grain max loads. Stay together better with less framentation.
Don't get caught up in the foot lbs. of a muzzleloader. Big slow bullets KILL. As the buffalo that were almost wiped out. Look at this link to see another theory about how big slow bullets do the job:
http://www.loadammo.com/Topics/July02.htm
go to the powerbelts website and they have balistics charts. I feel very comfortable with 95 grains 777 with 405 grain powerbelts out to 120 yards. My max on elk with open sights (required by Colorado) is 100 yards.
I like powerbelts and have found a good, accurate load, so I will probably stick with that, but I may also try the 460 grain no excuses conicals. Have not heard anyone say anything bad about them for both accuracy or performance on elk.