bitflipper
It sounds like maybe you're putting your music onto a CD and then comparing it to radio broadcasts in your car.
That's exactly what I'm doing, and I'm finding that different stations broadcast at different volumes. The local country station (about 25 miles away) sounds comparable to my stuff (since my mastering experiment began) while the local rock station (about 5 miles away) is much louder and pushes more bass. But I also have a home theater on which I can just load my tests onto a flash drive and listen to them on it, as well as a cheap boom box.