Bass 12s will probably sound gash, no top end an the wrong sort of speaker breakup, no mid hump. Is the problem that you are trying to get driven tone from a powerful clean amp, or not enough volume? Bass speakers will likely be less sensitive giving you less SPL for the power, so less volume, but means can push amp harder, but their top end roll off will filter out the harmonics from the drive, so you lose again.

The speakers are the bit that makes volume, if you have more than enough volume, but they are breaking, turn down. More likely you are pushing too much low end, rigging a high pass would be best. hemp isn't an inherently strong cone material (otherwise PA drivers would be made from it), just a stronger speaker would be better (higher Xlim on the spec sheet), but you have to trade off sensitivity, a 3db drop in sensitivity means you have to push twice the power for same volume, so if you get 3db more sensitive speakers, you'll need to push half power for same volume and overpowering them shouldn't be an issue.