There is no way to improve a recorded signal but 100 ways to make it worse. The best you can do is to amplify it in the preamp and to send it out with high gain to the amp.
GAIN ON PREAMP VS GAIN ON POWER AMP
What gives better sound and or control of the bass. Increasing the gain on the preamp or increasing the gain on the power amp. Either way would you hear difference in sound quality?