The CX300s are your best choice for cheapy phones. The NewEgg deal is legit, they are an authorized dealer. As far as ebay is concerned, assume ALL CX300s on ebay are counterfeit. I dealt with this with CX500s, I have a legit pair (from NewEgg, actually) and a counterfeit pair off eBay. I don't have pictures right now to put up of the differences, but here is how you can evaluate fakes:
First the packaging: two things. The whole cut to hang the package on a shelf rack is tremendously ragged and not smooth. If you stick your finger in it, you can penetrate the package, as the two plastic shells don't seal there, which is a dead giveaway. Second, if you look at the bottom of the package, there is an embossed “<PET>” stamped into both the upper and lower plastic. The lower plastic is embossed very poorly, as if done by hand, it should be crisp. Next, the cardboard insert: The text is not bold and it should be. Additionally, the packaging color is slightly off (should be more blue-green), and if you look at the male model’s eyes, on the real version, you can clearly see a white sparkle from a camera flash. A reprinted (counterfeit) version does not show that. Now onto the inside: The actual case that the headphones come with should have a shiny embossed “S” for Sennheiser on it. The counterfeit is embossed, but not shiny. Second, the case's flexible metal opening mechanism is very flimsy and doesn’t work well, while the real version is VERY stiff and functional. The packaging that the earpieces come in is different too, different shape bag with different printing on it. The fakes have tall, thin bags, while the legit version is squat and wide. Finally, the headphones themselves are difficult to visually differentiate, except for one key difference. Where the wires from each ear join comes together, there is a plastic piece that says “CX500.” On the authentic Sennheisers, the CX500 is written in very thin, fine font. On the fake versions, the writing its thick and bold. I hope that helps anyone else out there who may have been duped. Cheers.