I've got a lot out of reading others' reviews and suggestions. Recently I spent a lot of time choosing portable headphones. I'm not an expert, but I have a lot of listening "experience" so I'm sharing my experience in case it might help others. First, my definition of portable is being able to walk around with just my iPod, that is without a portable amplifier. I ended up with the Sennheiser HD 598, which are comfortable and sound great (good detail, warm with modest bass), but with no offense to Europeans (the design is inspired by their sports sedans) I wouldn't wear these in public. I'm actually amazed by the sound quality connected directly to my iPod that I'm considering selling my HD 650 headphones. They are better used with my NAD receiver, but I really hate to be tethered. As a bonus, although Sennheiser doesn't publish this, you can call them and order a short cable with a 1/8" plug for $15. So other than the bulk, they're really great portable headphones, just a little more noticeable compared to on-ear headphones. I was hoping to find satisfactory on-ear headphones as I'd like to use these throughout the day, so I listened to the Sennheiser PX 100, PX 200, HD 25-1 II, HD 238i, and Grado SR80i. I tried the Grado based on rave reviews, but I found them too bright, almost harsh. I tried the HD 25 also based on reputation. I found them uncomfortable, and even for on-ear headphones, completely closed. Good for noisy environments, but otherwise the HD 598 is far superior. The PX 100 and 200 sound good, but other than foldability, the HD 238i is sounds better. Although no comparison to the HD 598, the HD 238i sounds great, just a bit muddled with weak, but decent bass. And the HD 238i are so comfortable, you can forget your wearing them. My only complaint about the HD 238i is the connector was loose on my brand new pair and the sound would cut out on the slightest touch. I sent mine back for replacement, but I've read that it's a common problem. If my next pair is bad, maybe I'll replace the connector myself. These would be my first choice for outdoor use, like at the pool where it's not too noisy. And for my backup for, as comfortable as they are, when I tire of wearing the HD 598.