They are all really tough to get to tell the truth- generally much harder than NY/DC biglaw if you are not from DU/CU. The problem is they don't have large class sizes like firms in bigger markets. The fact that you are from Denver helps (in fact it is almost a prerequisite), but you are going to need some serious grades to seal the deal.
Definitely apply for a 1L clerkship (despite the fact that it's pretty much futile) for the reason of establishing your interest.
As for starting salaries. The 160k firms are only going to hire 1-2 a year, if that. The firms with a big Denver presence (Holland & Hart, Fagre, Shearman & Howard) will have larger class sizes, and are therefore a more reasonable goal.