Assuming theyre dual voice coil, both coil at 4ohms, you could:
both coils in series (8ohms), subs in series (16ohms)
or
both coils in series (8ohms), subs in parallel (4ohms)
or
both coils in parallel (2ohms), subs in series (4ohms)
or
both coils in parallel (2ohms), subs in parallel (1ohm)
If you can find a mono amp that can run 1ohm stable, go for that, otherwise go for one of the 4ohm examples.