I bought a small, inexpensive Uniden 520 and it works great. I used to own a 4' Firestick antenna that worked well, but it was too long and hard to tune. The 3' Wilson that replaced it works just as well and tunes much easier. $40 for an antenna is pricey in my opinion. You can get the Wilsons for about half that much.
As for having a CB on the trail, I think it's very important when in a group of wheelers of varying experience. The group leader can communicate to the rest of the group certain things about obstacles (hard or easy lines, bypasses, etc), what to watch out for, or when bikers, quads, or people on foot are approaching the group. Same for the trail gunner, who can report on a broken rig to those in the front of the pack.
As for tuning the CB, you want to tune it using at least several channels spread out across the spectrum. Also, your vehicle plays a huge role in tuning; therefore, placement of the antenna is very important in the radio's ability to receive and transmit.
If anyone gets only 4 miles range out of a CB, they probably need to tune it or replace the faulty/substandard part. When I was in Moab I was talking to a friend who had just crossed the Arizona-Utah border. It was crystal clear, too.