10 inches my boy, use it well. I think that going for 1x10 will be better (and tighter sounding) than 2. The soundwaves from 2 speakers will cause independent nodes and antinodes, so you'd have to position it perfectly for you to hear it; any shift could move your headspace into a node, reducing sound quality. Forget about passengers tho, they stand little chance of hearing the good quality. Now I know that this is difficult enough physically speaking with 1 woofwoof, but it would certainly be easier than 2. So if quality is what you want, fine-tuning a single unit will be better. If you want to shatter your teeth and get buxom boosoms bouncing, 2 is the go.