2 ohm, is just the impedence of a speaker, has nothing to do how loud they are. You need to go read up on Ohms law, because it is to lengthy to explain in a post.
More power doesn't inherently mean something will be louder //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
And even assuming you had two speakers with identical efficiency and power compression, doubling the power would AT BEST net you an increase in output of 3db....which is only "noticeable". Not a drastic difference by any means.
Long story short; Pick a speaker based on it's sound, not it's impedance.