Do the newer iPhones work with any portable USB DAC Amps using the camera dongle, or do they need to be designed for iOS? Thanks!

Hi, I'm upgrading my speakers with some polk audio 6x9's and 6.5's. Can anyone comment on the differences, be it technical or sonic, between th DB and DXi sereis? I'm also looking for a conservative amp that'll simply do the trick. Any help on either subject would be greatly appreciated, thanks!

Hey everyone, using the HD 25-1 II as a reference, what would be the next step up? I can't imagine having too much quality time with open headphones so closed is a must. I primarily listen to hip-hop, a good deal of classic rock then a lesser blend of metal, techno, alternative and country...