Regarding earbuds: did you try old MX300/MX350 buds back in the days? If you didn't like them, then there is no point spending money on Yuin's, but if not - try Yuin PK2/PK3. Pick one matching your sound tract (one is 16 ohm, one is 32) and give it a shot.
For the Sony's - I can't call them HiFi, bass is too pumping, I'd say. Sometimes I barely can hear anything except for the bass, if frequency is too low. I don't really know if it's just my ears trying to save themselves or the driver is doing some low HZ, so no way to reproduce high frequency.
After I finished that post, I decided to plugin my old HD555's, and... oh dear, it so clear, crisp and flat, can listen forever. I don't really remember, but I believe they are old 120's. I primarily use 'em with Kawai digital piano and definitely will not be replacing them with bassy Sony's.
Then impedance is 24 ohms... I have 7g classic which has standard sound tract for 32 (stock buds are 32 ohms), so it's not a fit also, unless I want to crack the pod open again to put some heater in it to match the impedance to what amplifier circuit was designed for.
Again - these headphones are not HiFi/reference gear, you either like them or not, but for 300.. you'd better do.