So I pulled the trigger on a pair of HD 558's and am eagerly awaiting them from Amazon Prime.  

How is the sound signature on the k550's? I would imagine kind of similar to the M50's in theory since they're both closed back? I have heard the hd 558's and I liked the top end so I would imagine the hd 598's only improve everything on the 558's?

Hello Head-Fi!   Hey guys, I'm new to head-fi and new to hi-fi equipment as well. I've been looking at the forums for a while now. It was because of these forums I bought my ATH-M50s and love them. However, I'm looking to buy a Christmas present for my girlfriend who has never owned any...