I owned Sony EX300 before I purchase this upgrade. I considered UE700, Monster Turbine and Sennheiser CX550 and tried all of them seriously. I dropped UE700 out of list first, it didn't offer enough bass for me. To be honest, I like the sound signature of Monster turbine the best, however it's over my budget. At last I chose CX550, which was the closest choice under $120.
Like CX95, CX550 need serious run in to get satisfactory performance. After 300 hours of run-in over 3 weeks, the bass got tighten up, with considerable bounce back in the mids. I can feel that the sound quality of the earphone is still improving.
This earphone is good for the bass lovers but it may not be the best choice for classics, however I did found cello to be very enjoyable to listen to with this earphone.
For those who always travel around, ask yourself a question: Can you stand hearing your footsteps? I can clearly hear each step of mine, every move seemed to be amplified on this earphone. As for isolation, it cuts off ambient noise reasonably well, but it never reach the level of "room silence" on the streets.