I don't know if it's safe to turn the volume up all the way. I have a subwoofer with it but do not have the option to change the volume on the sub. The stereo says it's 150 watts. And "AC 120 V~60 Hz". I have 2 speakers that say 6 ohm. And the sub says 4 ohm. I have no idea what any of this means. >.<. and do you think it's a decent stereo? Thanks so much, help would be greatly appreciated. By the way the speakers and sub came with the radio stereo thingy. Thanks 