Compared to most other $300 consumer headphones, the K550 are definitely less bassy, but I think it if you can get use to em, you may find you really like it. My friend who owns them says it took him about 2 weeks to really start to enjoy the sound (& now he says all bass-heavy headphones sound muddy to him lol). Andhe's totally a treble-head now. You should also add try to demo the Sennheiser Momentums when you're at Best Buy!
There's also the Yamaha Pro 400/500, but I wouldn't personally recommend them. Since they basically ripped off the Beats design, if you thought the UE6000 looked gaudy/beats-like, there's probably no way you'll like those.
Less portable but how about the Mad Dogs at $300? I personally can't think of any other competitors to the MDR-1R at the $300 range, but if someone else can, I would love to hear about other opinions! Or maybe you should try getting a different pair of MDR-1R as it sounds like not everyone experiences the build quality issue that you had, so maybe it was just a bad batch?
Mad Dogs are good, but I wouldn't dare classify them as portable, both on style and amplification requirements.