the only difference it makes is what your amp can put out. a general rule of thumb is if an amp is rated at 4 ohms your output would double at 2ohms and be half at 8 ohms. not a perfect rule but usually close. ie my Rockford Fosgate P3001 is 150w rms at 4 ohms and 300w rms at 2ohms. If I had an 8 ohm load it would be about 75w