Check out RadioReference.com A lot of departments have gone to the Digital Frequencies and I believe Allen and Plano are one of them so first make sure it picks up Digital. I had purchased a RadioShack scanner that did but I don't believe I ever picked up Allen. With the Digital frequencies they now have the ability to block being listened to. I wound up returning the scanner.
The website I listed is a great resource and they keep up with and list frequencies for you. There are a lot of heavy duty users on their forums so you'll certainly see some reviews etc. there.
Oh, it doesn't appear that Radioshack has scanners anymore.
