So a few years ago I sold off all my compounds and went to a crossbow.  

I only have 1 left a Diamond edge that adjust from 5-70lbs.

Now planning an Elk hunting trip this fall to Colorado.

What bow should I look at for this?  

Will most likely use 2" rage 2 blades, since I have a pile of them.  

What arrows you all using for Elk?

Basically anything. My go to right now is the Elite Kure, as I enjoy its "SET technology" feature for easy, no-press-needed tuning. Bowtech has a similar technology.

Please consider a cut on contact head like the Magnus line. Leave the mechanicals for the east coast standard poodle sized deer.

There's a few mechanical heads I'd say are ok but a 2" rage on an elk definitely isn't ideal.
my setup out of my elite is
30.5dl
420gr gold tip pro hunter
100gr slicktrick
303fps
compared to what a lot of people are shooting these days it's considered light but it works for me

It’s generally recommended that whatever you’re shooting impact with around 65 ft lbs of kinetic energy for elk.  

That being said, I shot the following:

100gr broadhead
484 gr arrow
70lb RX-3
~270fps
78 ft lbs of KE.

Shot placement, as always, is critical. Plenty of elk taken with mechanicals but you have to do your job in placement. Don’t hit the shoulder blade. I’ve actually seen a mechanical not penetrate a deer’s shoulder blade. Elk are only tougher. If you’re confident in your ability to place a mechanical in the boiler room, by all means use it.

Ditto the cut on contact broadhead.  And tune your arrows so they fly straight bare shaft.  I've come to the conclusion that cut on contact sitting on a tuned arrow is primo.

A few things to cover here, first the bow.

Top 5 this year will be the Mathews V3, Hoyt RX5, Bowtech Solution, PSE EVO EVL 32, and Elite Enkore. Do some looking into each one, and find a shop that has one or more and go shoot it if you can. Thats really the only way to be positive you like it.

Sight. Spot Hogg is my choice, very solid and bright, with great options. Grinder for a regular fixed 5 pin, Fast Eddie for a slider. Black Gold is another popular choice.

Rest. Hamskea is the top of the game for limb driven, QAD seems to be the best for cable driven.

Arrows. This is the piece that could go a lot of different directions. Ideal total weight for me is 450-500gr total weight and 10-15% FOC. So your GPI is pretty important if you have a specific goal. I currently shoot Easton Axis 5mm arrows with 300 spine, 10.7 GPI with 175gr total weight up front for a 12% foc. Easton is a solid arrow choice, but there are other options as well, Victory, Black Eagle, Gold Tip...maybe more but those are the ones I can think of.

Broadhead. Mechanical would be my absolute last choice for elk. A fixed blade cut on contact is the ultimate for reliability and penetration. I have shot QAD exodus before, which seems to be the top replaceable blade that has nearly cut on contact performance. I will be using Iron Will 125gr broadheads this year with the bleeders. I also have the Iron Will insert and collar system behind the broadhead for more weight and strength at the front of the arrow.

Broadhead tuning will be the most important step in your setup phase. Making your field point and broadhead fly with each other at all distances will mean your bow is happy, shooting straight, and the shot is efficient. Paper tuning is a good start, but bareshaft at distance and then broadhead, will be the final step.

Another small but possibly important thing is the peep, obviously it needs to be sized for you and your sight, but the shape and design can be a noticeable thing as well. I got a Hamskea raptor peep this year and it's awesome. It can handle a little twist and helps cut down on any glare. I went back and shot my old bow with a standard peep and wouldn't go back to that style.

I'm somewhat obsessed with archery so I like to get really into the details of stuff, but this is as quickly as I could give an overview of my thoughts on a full setup.

The advice in the post above is good.

I'm not an elk hunter (whitetails here) but I'll simplify it even more. If you are shooting a modern compound of 60lbs or above with a moderately heavy arrow, cut on contact head, a good tune, and are confident in your abilities you are capable of taking an Elk. My arrows come out to about 440gr with a 100gr head and IIRC 12.4% FOC. 340 spine, 28.5" @63-64lb. I see no need to go any heavier with modern equipment on deer and like quality mechanicals for whitetail. That said, I won't shoot a Rage and would not use mechanicals on larger species.

Whitetail are pretty easy to kill with good shot placement, and modern equipment, this isn't the 90's anymore. Back in the day i was shooting an Oneida AeroForce x80 at 80lbs with heavy arrows. Even if I wanted to shoot heavy setups like that now there is no reason to with today's tech on all but the largest animals. YMMV.

I am elk hunting Colorado this fall and just picked up a new bow. I found a good deal on last years Hoyt RX4 Alpha. It gets delivered tomorrow.

So how is the bow ?? Assuming it got delivered.