There are two amping challenges/things amps can help with headphones.
1.) low impedance headphones (like 32 ohm headphones made for iPods, most common today) benefit from a large pool of Current to draw from (at listening volumes) in order to prevent distortion and clipping problems (harsh highs and flabby bass, etc).
2.) High impedance headphones need more Voltage to be able to sound loud enough, but usually they have plenty of current at listening volumes.
A headphone's sensitivity and an amp's "clarity" and design also plays a role in "loudness" and quality, but to keep things simple and speaking in a general sense, a higher Ohm headphone will sound great as long as you can amp it loud enough (and your amp isn't really cheap/crappy/colored).
The K612 has 120 ohms impedance, but it was plenty loud from my Omni and my Turtle Beach DSS. 120 Ohms is higher than most, but it still benefits from a clean amp that also supplies plenty of current. If I lost all my headphones and I wanted a good price value that would be great for years, I'd buy a K612 too.
Some people will just dislike no matter what though. I can understand people disliking hit detection or graphical styles, I only think people are just being ignorant if they get mad at Bungie for "favoring Sony" and "abandoning the Xbox community that made them." Bungie was a Mac-only game dev, then they were bought by Microsoft and much of what's happened since then has been influenced by 3rd parties. I'm glad to see a new IP.