The Superstar 121 is a single final radio, should do maybe 25 watts peak after a clean tune. Whitenight, there is a log list of things to check. First up, Antenna system. Make sure the antenna and coax can handle the power. make sure the install is good and your SWR is nice and low. Next up, the amplifier. Does it even work? is the install good? Are you running a good jumper thats 3 or 6 feet long? Last up, the radio. Set the AM dead key on Lo at 2 watts and if the tune is proper with nothing clipped you should get 20-25 watts peak swing easy. Thats plenty to drive that amp to 450 plus watts. You will need a decent external watt meter to test things out. Make sure your vehicles battery is good and the alternator can feed at least 60 amps to that Texas Star.