First off-
Any of those bullets in factory loadings will work.
If I were you, I would try to get over the notion that you are going to take your '06 elk hunting with 500 yard targets in mind. Unless you are planning on hunting on total windless days, which are rare in most elk country, wind drift must be taken into account, and understood. i would suggest finding a big prairie dog town, hit it on a windy day, and get a sense of what wind actually does at ranges of 200, 300, etc. ranges. It will make you a better big game hunter, in my experience. If your quarry is found in deep timber, then it's a whole different game- I've killed more elk in timber than in wide-open meadows or fields, especially later in the season when they have been pressured.
I would also ditch the 4-18X scope, and mount up something with less magnification and lighter weight. You don't need Mt. Palomar to go elk hunting.
If you prepare for shot opportunities out to 300 or so yards, in my own personal elk hunting experience you will be ready for the vast majority of situations afforded to you, if you are lucky. I have hunted and shot elk for most of my fairly long big hunting career, and can only remember two that were taken at ranges in excess of 300 yards, with the rest all taken from 50 yd. to 300. In that time, I have never had to track a wounded elk, but I always take what I regard as a certain shot.
Colorado is a great elk state, but keep in mind that hunter success is around 20%- if an opportunity presents itself, you'll want to make the best of it, and a lot of factors are way more important than bullet selection.
