If given the right box, I have no doubt you could achieve your bandwidth and SPL goals with the Peavey driver. The problem IMO, is that I doubt the published T/S parameters are very accurate. Peavey isn't well known for dead nuts specifications. Assuming the published specifications are accurate enough, we would still need to know more specifically which black widow you have. I'm aware of potentially as many as 3 18" woofers from peavey under the black widow name. A 4 ohm woofer, an 8 ohm woofer, and a "low rider" variant with a longer voice coil often sold as a "subwoofer" class driver.
Considering the amplification available, alternative driver options may be more appealing because you could achieve your SPL and bandwidth goals through driver displacement and amplification, rather than through box volume and box related gain. Trust me, the black widow you have can play over 100dB @20hz in the right box, the issue comes down to whether it's worth having a monstrous and complicated box to build, especially with thousands of watts of amplification available that could be used to overcome the inefficiencies of small box high driver displacement designs instead.