HiFiMAN's RE-600s are a great pair of in-ears, outperforming the more established competition on a number of very important aspects. Getting a pair of in-ears to display such a broad and deep sound stage as the RE-600s is a great feat of engineering that requires a lot of attention to detail. While they do perform better in this respect than the Westone 4Rs and UE900s, they still manage to keep up when it comes to detail and linearity. But HiFiMAN's tips and the cable design were a letdown—others simply do a much better job here in terms of usability and comfort. This is a great conundrum: How can a company that nails sound performance not create a great set of tips, or a good cable? There is some reason behind the choice of cable as you can use it without an adapter if you are one of the lucky few to own a HiFiMAN HM-901 player, but most will have to use a TRRS to TRS adapter, which is a pain because it adds unnecessary bulk to the solution.

The RE-600s are definitely a step up from the RE-400s, but the price increase is not fully warranted. Yes, the sound stage performance is better and the sound signature is more mainstream, with a hint more bass. The RE-600s will definitely be a brilliant step up if the RE-400s were too bright for your liking.