Why buy an 8 ohm sub?

I have recently purchased 2 10" Kicker Comp 8-ohm subs for the simple reason that I already had an amp that matched the power rating for the subs at a 4-ohm load (amps rating). The amp will put out about 800w @ 2-ohm and 400w @ 4-ohm load (rms values). By running 2 single voice coil 8-ohm subs wired in parallel you are effectively cutting the impedance in half (8 + 8 = 4-ohm in parallel). To do this you simply connect the positive terminal of one sub to the positive of the other sub and then to the positive of the speaker output on the amp. Same with the negatives, sub to sub then to amp. Had I purchased the more common 4-ohm single voice coil subs my load to the amp would have been 2-ohms and too much power would be getting to the subs (100 watts more rms power than the peak power the subs could handle). I did this because of the space I had available and also because the Kicker Comp has performed well for me in the past as an entry-level woofer.

Hope this helps!