Should be fine.  Adorama has had them for slightly under $300 a couple of times in the last 6 months (on slickdeals), so this is a good deal but not too good to be true.  Enjoy the new phones!

I bit the bullet and took the foam from behind the drivers off last night.  I was expecting a more drastic change but it was pretty subtle.  Still sounds like the 650, which is great, but with a tad more openness and clarity.  Nice. 

Removing damping behind the driver is only going to bring that hump up. These mods are reversible if you are careful not to ruin the material when pulling it out, though it will take some care and patience to get it back in properly. You can add further damping behind the driver or in the cups to reduce the hump, but that might make them sound too overdamped or even off in the treble (glare, grain, etc.).

Removing damping in front of and around the driver, front side, will reduce that hump, and possible some of the low bass, and may also make the treble weird.

A year or two ago, I took the plunge into headphone addiction. I had various lower end headphones and some Sennheiser HD555s. Those got the most use, and I didn't believe I needed an amp. After all, I didn't need more volume than I was getting.

But I found Head-Fi. I bought a PA2V2 amp and my eyes were opened. My wallet opened even farther.

I dove in and got the Sennheiser HD598 and tried/returned a dozen headphones, with my favorite returned can being the Beyerdynamic DT880. They were a little bright for me and the earpads didn't quite fit my annoyingly tall ears.

Finally, I saw the price on the Sennheiser HD650 "crash" down to $400 when it was usually closer to $500. I bought them.

I absolutely loved what I heard. I couldn't get over how good they sounded. I used them with the PA2V2 and no DAC to speak of.

Then they sat in their box. They clamped so hard that they got uncomfortable, and they didn't sound better enough than the 598s to dig in the box every night to get them out.

I picked up a Creative X-Fi Titanium HD sound card because I'm a gamer and thought I'd try that out with my 650s. They sounded even better from that sound card than the PA2V2.

I then decided I'd use the expensive monsters and decided to bend them out until they weren't super clampy. It took a certain amount of bravery to do that, but I eventually got them to the perfect tightness. Then I bought an O2 amp and fed it from the RCAs of my X-Fi. The sound got better again.

I'm several more amps deep and many more headphones along now, but I'm still amazed at the sound of the HD650. I live in closed, semi-closed, and IEM land all week at work. When I get these open headphones on each weekend, like I'm doing right now, it's like breathing in the crisp, fresh fall air first thing in the morning.

Now I'm diving even deeper into the danger zone and looking for a tube amp. My wife is gonna kill me.

I wonder if anyone noticed my question buried in this thread. Has anyone tried the brand new box version of the hd600 and notice any improvements over the last version with the standard big black box? If the hd650 have improvements then the hd600 must have some as well, wouldn't you guys agree?