The bass of my k550 did enhance after about 40 hours of burn in, but not of significant quantity. It probably was the right decision for you to return them. They are indeed reference like, and with that said very flat sounding. I would recommend you to see a local dealer and just try out different cans. If you like to upgrade to a bassy headphone, take a look at Audio Technicas Ath-M50's or beyerdynamics.
Hello, From personal experience i can tell you that the HD598 are indeed well suiting headphones for you, especially for home use. They are not very suitable for portable use though due to sound leakage. About the cable, yes, you can simply buy an extension cable if you chose to buy the Sony's
The Sennheiser HD5XX line might not fit your needs as they require an amp to sound good and also they're open back, which means sound leakage and no isolation.
The M50s are always a solid and very common recommendation for everyone in a similar to your situation.
For your musical preference I would personally recommend you the Ath-M50s, the K550 are very big and more meant to be used at home. If you have loud environmental noise around you a stronger bass response would fit you better. My K550 lose the 'punch' whenever i use mine in the bus.
The long cable comes in handy at home, but for mobile use i mostly keep the biggest part tied up.
The seal does play a very important role on the K550. Though i have a big head it still takes...
A very clean and great sounding headphone is the AKG K550 which I have right now. They blow away all my previous headphones (including the portapro). Other than that, can you tell if you will be running the headphones through an amp or straight out of a device? You need to consider the impedance of the headphone before you make your final decision. Also, Open or closed-back?