Absolutely! In these large cabs, the second driver is really only needed for very high efficiency to get the most out of SET amps and/or high SPL and/or if tuned low enough [or sealed] for pipe organ symphonies, movie LFE tracks. Backed into a corner, it typically isn't needed, just as you say, nice to have.

Having someone over who's used to seeing a low efficiency [sub] woofer[s] work itself to death, go looking around my room for a sub because you can barely see the 515s move on most music, movies even at near 'Headbanger's Ball' SPLs.

GM