i had an amplified antenna. It didnt help. The JVC headunit I have in my truck now receives just fine. The Jensen however I have in my car is horrible. I havent had any problem with brand name radios. Its when I went cheap is when I was running into issues.
The aftermarket one I had really sucked to be honest, and blew in the wind at 60mph. Reception wasn't as good but it was just as long. I have seen a few people run 2ft Firestik antennas, not really sure on how the reception is.
Travis- you might want to check the conections for the antenna to make sure they are clean and tight. Also check the radio and the antenna base for a good ground connection.
Amplifier might help, but it will amplify the background noise too. Winegard generally makes good stuff: