
The HD 558s are the direct upgrade to the HD 555s. It will expand on soundstage as well as the bass. They go for <$145. If you loved your 555s and want to upgrade just a bit more 558s is the safest bet within your budget. Very similar construction, comfort is great, but Id recommend just going for the HD 598s, the flagship of the series. Lowest price I've seen is around $170, but now they around $200.
Why must I say this again? I'm not looking for open back headphones. Please, read the OP if you're going to comment. It's just common courtesy.







