I have the mach 460 stereo, and the sound qiality is great. About 2 weeks afetr I brought it home, I started noticing the upper speaker on the drivers side window was making a sqeaky noise. I took it back, told em to fix it. They said they did. The next day I hear the sqeakiness again, and I call them back. They swear they replaced the speaker. I am thinking maybe there is to much power running from the amp to that speeaker, it sounds as if it's "bottoming out" Anyone else have this problem? Also, I am upgrading to the Mach 1000 system after I get taxes back. Does anyone have thi system? Can you tell me about the sound quality and wheather or not AC/DC Sounds good at full volume. I do the AC/DC test whenever I buy new equip., cause it rarely sounds good at full volume with all the distortion from the guitar.