We present an experimental study on supercontinuum generation with high spectral power density by using a commercial nonlinear fiber amplifier. This new approach consists in the simultaneous combination of the amplification of a pulsed seed signal at 1.06 microm and its peak-power-induced spectral broadening as the optical pulse propagates along the amplifying fiber. A 750-nm broadening from 1 microm to 1.75 microm with tunable spectral power density according to the amplifier gain level is obtained. Spectral power density in excess of 3 mW/nm is demonstrated.