As a fellow front ranger, yes I feel a 4wt is the perfect rod for the front range. 8'6" or 9'. I went down the short rod road for a while under the perception of I fish small streams alot and need a shorter rod. I find I take my 9' 4wt in a lot of places I bought a short rod for and I dont have issues.
I currently run a Sage Z-Axis 9' 4Wt,which is a little faster so I use it on bigger rivers, windier areas. I also use a St.Croix Legend Ultra 9' 4wt I use for a lot of nymphing. I also have a Sage TXL 7'10" 4wt that I like a lot but I find I don't use it much now that Ive rekindled my love affair with the legend ultra.
Really any Med-Fast 9' 4wt will serve you well
From TFO,Elkhorn,Redington all the way up the price range to Sage Circa, Winstons etc etc they will serve you well.
Truth be told I spend alot of time with a 3wt rod in my hand. A broomstick 3wt like the Sage One I would have no fear taking to Cheesman, Deckers, Blue etc etc. I would only really fret going to a 5 or 6 wt if I hit the Dream Stream, Grey reef etc etc where you will run in to some real pigs.
Moral to the story I pick my rod based on
1) What I will be throwing, single dry, dry/dropper, Bigger hopper/dropper , streamer
2) Size of fish known to be in the river...I wont take my 1WT to the Northgate Canyon for example
3) WIND !!!!!!!!!!
I landed this guy on a 1wt no problem, 17" little fatty
And this stout one out of the blue on a 3wt TXL