This may be of no use, but i currently use an MXR Distortion + with a Concert BASS (not the same , i know) but it acts as a volume boost and the distortion really cuts through. another pedal i've used before was the ProCo Turbo Rat, which also gave me a boost in volume.
also, have you tried using the footswitch for distort/boost on the concert lead? i got a fender two-button footswitch w/ rca inputs for my concert bass, and the increase in volume and fuzz blew me away. before using the footswitch i was turned all the way up and could barely compete with the rest of the band, but after i could turn down to 6 or 7.