It's important to understand what you mean by 'something with more low end'. Are you looking for more prominent bass or deeper bass. Many fail to recognize the difference. Very probably either of these can be achieved by retuning the cab ( by changing the number and length of ports, or by sealing - for a ported cab, or porting for a sealed cab). You can try some of this yourself, listening to and evaluating the results with respect to your target tone. Watch cone excursion, particularly on the upper half of the A string. Retuning can alter the excursion limited power handling of a cab.
Changing the drivers will land you in the same position: needing to optimally une the can, and potentially dealing with less excursion limited power handling. Changing drivers is a major redesign of the cab with respect to cab tuning, mids, excursion limited power handling and blending with the horn. To get deeper bass, you will likely have to sacrifice maximum volume (the cab will produce less volume).
