Grado SR225i
Sound: 4/10 - When I first got these, I was in love. They were my first pair of hi-fi phones. However, after getting HD600's and properly amping them, I immediately wanted to sell them. They did not improve at all with amping for me. They sounded harsh and sibilant. They were refined and detailed, but unlistenable for me. I fully understand why everyone likes these for rock. They have no soundstage and they make guitars sound up close and loud. I personally like more laid-back phones.
Comfort: 2/10 - Worst I've ever used. I tried bending the headband until the bowls were comfortable, but then the sound suffered. I ended up just putting a beyer DT770 headband and sennheiser hd414 reverse-quarter modded pads onto them to make them wearable for more than 3 hours.
Build Quality: 8/10 - Surprisingly sturdy, all things considered. They seem like they would've lasted for quite some time. They're fully plastic. I took two points off because of quality control at Grado. Mine came looking as if they'd been thrown around a bit and weren't properly in the pizza box.
Overall: 3/10 for the price. I found these MASSIVELY overpriced, which is probably why you'll see so many for sale for $140. They're good headphones if you can stand them - don't get me wrong. But for what you get it's just not worth $200.
Sennheiser HD600
Sound: 10/10 - The moment I had these properly amped I knew what I had been missing with the Grado's. Ahhhh, warmness. These are laid back, warm/darker, have a very good soundstage, and are pretty well balanced. With these music just kind of floats around your ears, caressing your pinnae and teasing your malleus. It's like a seductress rubbing up against your cochlea. My kind of lady, er, headphones.
People will tell you these are best for classical and jazz. Allow me to disagree with them. I think these are fantastic for rock, metal, jazz, classical, acoustic, etc. They work perfectly with all genres. However, if you're in the Grado camp I can see why you wouldn't like these for rock/metal. They don't inflate the highs so the guitars and vocals can be in your face and loud.
Comfort: 9/10 - Very comfy, but there is just this SOMETHING that isn't working with them. I can't tell quite what it is, but I'm always trying to adjust them. For non-lunatics this should be a 10/10. I love the clamp.
Build Quality: 9/10 - They seem like they'd last. In fact, I know they will. My current pair has been through at least two other owners. I took 1 point off because of a couple of small things. The pads having to be replaced a tad more often than I'd like and the headband being pretty easy to break.
Overall: 9.5/10 for the price. These really are amazing. I bought mine for $175 used. They do not sound like $175 headphones. They sound ridiculously good. I cannot recommend more.
AKG K701
Sound: 9.5/10 - Let me just begin by saying that I think these cans are massively underrated. They're often criticized for being too lean on the bass. I understand this criticism, but do not agree with it. I think the bass quantity is plenty - and you're hearing this from a fan of the HD600's! These are absolutely on the bright-end of the spectrum. They are also VERY, VERY, VERY detailed. VERY. They have a bigger soundstage than the HD600's, and a very interesting one at that. Vocals are kind of upfront, guitars are more on the sides and further away, bass is all around, and drums + cymbals are further away. This may not be fully accurate, I find it difficult to explain. These cans seem to work every genre perfectly, much like the HD600's. The one criticism I have with them are vocals. Female vocals sound a bit flat and lifeless with these, male vocals are a bit better. By no means do I mean these RUIN vocals, it's just that they're not perfect.
Comfort: 9.9/10 - They lose .1 point because of the bumps in the headband. They're VERY comfortable and ENORMOUS! I find these to be more comfortable than the HD600's. They give your ears a lot of breathing room. The bumps at the top of the head can be annoying - but only if I rub them *Hard* into my skull. I need to try these on after cutting my hair (It's pretty bushy up there) to see if I have to lower this rating.
Build quality: 7/10 - plastic plastic plastic. It peeves me that AKG didn't even make the tiny little GRILLS out of metal at this price point. The cord termination can-end seems pretty good. I took most of the points off because the auto-adjustment parts of the cans seem VERY flimsy. They should've been made entirely of metal.
Overall: 9/10 for the price. I bought these for $5 more than the HD600's. They sound very similar in terms of overall sound quality and refinement. I like to think of these two headphones as brother and sister. The Senns tilt towards the dark end, the AKG's towards the bright. However, the HD600's are absolutely more enjoyable. The K701's are a tad analytical, but I can still enjoy them.