A couple of ideas before you buy a new radio….
Power your radio directly off the battery. This will help eliminate some sources of noise. Modern vehicles have a lot of computers that can generate a lot of RF noise. Tapping into existing wiring or cigarette lighter sockets is a great way to get all that unwanted noise into your radio.
That noise/interference is going to make it hard to hear the weak stations. So, if you want to talk skip, don't forget that it works both ways, you need to be able to HEAR as well as TALK.
A preamplifier might be a good idea. It'll boost weak signals a bit and get them to your radio. If asked, I would have said that you shouldn't buy an amplifier without a preamp.
And, as methusaleh said, it ALL about the antenna. You take a $20 radio and a $50 antenna and it'll probably work way better than a $200 radio and a $20 antenna. Without a properly installed, mounted and tuned antenna you might as well get rid of the amplifier.
1. NO mag mounts. If you are serious about making this work, drill the hole and mount the antenna where it needs to be. That is, top and center of the vehicle roof. Anything else is a compromise. If you want this all to work well, but cut corners on your antenna install, you're just wasting electricity.
2. No gimmick antennas. Antenna design is governed by the laws of physics. NO manufacturer has a secret way around those laws. Doesn't matter what the package says, what your buddy says, etc. If you want it to work well, mount it as I said about, and use a full 1/4 wave antenna. 102" whip with the 6" spring. Base loaded antenna will work, but none of them will work as well as a real 1/4 wave whip.
3. Clean power. As I said above, power everything directly off the battery with properly sized wiring, fused, grounded, etc. If you are getting RFI (radio frequency interference) into your radio via the power feeds, it's going to wipe out some of your receive capability.
4. Grounding, grounding, grounding. Ground everything correctly. Ground the - power. Ground the radio chassis. Ground the amplifier chassis.
5. Decent coaxial cable with properly installed connectors. RG-58 isn't bad for CB use. There are better choices for mobile use, like LMR-200. Use -just- the length you need. If some guy starts telling you that you 'must' use 18 feet, 3 feet or some other length, ignore him. These are old wives tales spread by guys that barely know what end of the radio to speak into. Use -just- the length of cable you need.
Also, no twist on coaxial connectors. Use either crimp on or solder on connectors. If you do not know how to install them yourself, there isn't any shame in buying your cables pre-terminated.
6. Tuned antenna. Get a decent SWR meter. Don't rely on the ones built into the radio, they are often very inaccurate and low resolution. If needed, pay someone with a good meter to tune the antenna for you.
7. Avoid the noise makers. While I'm not on CB very often, the thing that annoys me the most is the echo boxes, roger beep, etc. Skip that crap and focus on clean audio.
Don't fall for the gimmick stuff. It doesn't work, and doesn't help. Focus on a good clean installation, clean power, tuned antenna. That'll make the biggest difference.
Amateur radio operators can talk around the world on 5 watts because they use the things I pointed out above. It works, it's been proven. Focusing just on RF power output won't help things. There's so much more than just running power.