I'm considering upgrading from RE2s to the RE0. I currently use Grado SR60i and the RE2. The RE2s are getting the most use during commuting to and from work. As a source, I use an iPhone 4. I also have a Fifo E5 that I occasionally use with the RE2. I am just wondering if I should expect much difference in the RE0? I will say that I have been happy with the RE2. I listen to all kinds of music. The reviews for the RE0 for the most part are great...the RE Zero are also an option I guess. Anyhow, any suggestions, recommendations or advice?