I bought these headphones because I needed a closed back design to keep my wife happy.At the time I had purchased the Sennheiser HD-598's based on all the positive reviews,however they just not have the bottom end I was looking for.
Well now I can honestly say these inexpensive cans have some serious low end! Keep in mind that we are talking about headphones for well under $100.The overall sound is also very good IMHO.They pair well with my iPod shuffle and play to some substantial decibel levels,as I tend to to prefer music very loud.
The Solid Bass headphones are not really designed to pair with an amp,although they do sound good they will run out of steam with too much power.
The biggest draw back to the AT-W55 is comfort.The initial clamping force was almost unbearable,but they have eased up over time.The pads themselves are comfy but after longer listening sessions my ears start to hurt.
I recently purchased some Beyerdynamic DT-770's and did an A/B comparison and the Audio Technica's blew them away as far as bass is concerned.
All in all I highly recommend these phones for portable use,however the clamping force will take some time to loosen up,but if you are a Basshead you will not be disappointed.with these cans..
