it all depends on your amp...say if u have a jbl 1200.1.....your amp can go down to 1 ohm, but i would recommend running it at 2 ohms if possible. IF you were going with one sub on this amp...i would go with the 2 ohm sub...if you were running 2 subs i would go with the 4 ohm subs and wire themd own to 2 ohms. Tell us what amp you have and how many subs you are running on it. There is no performance difference between 2 and 4 ohms subs...its just for better wiring capabilities.