Enhancing music and overall wattage from player to auxillary

I have a zen vision w that I plug into my work radio. I do construction. My first problem is volume level of songs on my player. One song is soft next one is loud. I recently have downloaded a program that I think will fix this problem. Second problem is in certain circumstances my radio isn't loud enough. The days that I work around heavy equipment, power tools, etc. Its not that my radio can't get any louder but the player can only put out so much. I have somewhat of a custom radio that I built that is capable of pushing out a 100 watts. I have had this system plugged into my pc and the player cannot, obviously, come close to pushing the same amount of watts. Question is, is there anyway to amplify sound coming from player before I get to radio. Thanx.