The BL9s would certainly be able to handle the bass, but the issue lies in connecting it.
Guitars, use a much lower line leval than say an ipod or a cd player, so they have to go through a pre amp first.
A bass/guitar amp overcomes this need for a preamp, because they were designed to handle this type of signal natively.
If you ever watch a video of guitarist such as Carlos Santana, he will always have a relatively small amplifier beside him, and this is then Mic'd and sent through the auditoriums sound system. This is because most of the characteristics of the sound are delivered by the amp, especially if it is a tube.