Yes, it is possible. I have heard of it being done, mostly in competitions. I personally wouldnt know how to hook it up, so hopefully you get more replies then mine.
as long as it is a dual voice coil and the same brand and watts, rms you will be fine SINGEL VOICE COIL WILL NOT WORK just think of it this way dual voice coil is like to speakers in one. but i am not sure if each coil is 800 watts max or 400 watts max on a 800 watts speaker lets say.