question about how a cb sounds

Alot of the "high end" radios such as Galaxy and Ranger (RCI) have echo controls on them. You can also get echo mics and echo boards for non-echo radios.
As for them sounding extremely powerful they may be running external power or amplifiers (kickers, perkolaters, seat warmers, ect.).

 

The radios you are referring to would be something like a Connex 3300 or a Stryker 440. As mentioned you can have an echo board installed in almost any CB radio though some like the ones I've mentioned come with echo and extra power built in.

 

There are countless radios with echo built in them. To name a few, Galaxy, Magnum, Stryker, Connex, General, Ranger/RCI, and more. They can sound good when set right but sometimes they sound terrible. You will only find echo stock in an export radio, which is not found at a truck stop, but rather a real cb shob. Alot of good exports out there, I own a few. They also put out some bigger watts than a Cobra will.