Not necessarily true. I find the Z5 to be warm not necessarily bassy. Depends on what you're running them out of, output impedance matching. Driving them properly I find them to control bass quite well. The imaging is simply world class and its like I'm in a chamber hall of music. At higher volumes it honestly sounds like I am wearing an over ear pair of headphones. The ex1000 doesn't do that for me. This is comparing them directly. YMMV
Sardar, try and audition them if you can. Have you had a chance to hear either the ex1000 or 7550? You might be surprised by how well the Z5 performs. I would say the EX1000 and Z5 are same tier but different but with a different take on sound signature. Like I said earlier, Sony is reading the market shift with more people getting into high end audio and peoples predilection for modern close mic recording, means that they don't want to give people headaches with hot treble.
Did you know that the angle of the dynamic driver tilt in the EX1000 is response for its treble tilt? Thats why they worked that out and its not present in the Z5, in addition to a conscious deacons to tune it a certain way. Truth be told, I LOVE how treble is handled on the Z5. Am listening to some Iron Maiden now and I love how the cymbal crashes sound. Z5 has super instrument separation and sound layering. It is kind of unfair to write them off not having heard it yourself, rather than repeating others impressions
My 2 cents [going by the weak ass canadian dollar, might not be worth all that much
]
Again YMMV and this is in my experience but I have been listening to the Z5 and EX1000 side by side, so I am able appreciate their differences.