150 feet? It sounds like your SWR may be off.. it should be a lot better than that. Like Uncle B said the Cobra 75 is a pretty nice CB, but more of your performance difference is going to be in your install and antenna.
What's the name of that CB shop again? there's a place that will test it for you, then help you make adjustments, etc. They'll also sell you what it takes to reach optimum quality.