"Just got my new Sony XBA-A2 In-Ear Monitors, about 2 days ago. Sound quality is insane, thumping bass that's detailed and punchy combined with full mid tones and crisp highs. Sounds much more rich and has deeper bass compared to the Sennheiser IE800's, though at a cost of having a not-so-flat sound signature with the raised mid-bass and high-mids. Mini-review below:

Day One of using these bad boys, right out of the box I plugged them into my PC and they sounded like a muddy mess. The bass was just booming, listening to 'September' by Earth, Wind & Fire I immediately heard that the bass just mixed in with the low-mids making instruments quite blurry with vocals melding into the background. Dissatisfied, I let them burn in for about 2 hours with some blues and classical along with some reggae.

Day Two of using these chunky IEM's, after burning them in for a little over 2 hours I decided to put them to the test again with 'September' by Earth, Wind & Fire; 'Breakout' by Celldweller and the classic 'Allegro Con Brio' by Beethoven.
To my surprise the sound was much more detailed after the burn-in, with different instruments being distinct and clear while the vocals were upfront and engaging from September.
The bass and vocals in Breakout was also really deep with the bass extending down to the lowest frequencies to the point where I can feel the bass, not just hear it, the vocal perfomance was strong with Klayton's voice sounding loud and intimidating while maintaining the clarity of the drums and cymbals in the background.
Now Beethoven. It sounds great, wonderful clarity and detail of the instruments such as the trumpets, violins and trombones all sound rich and full of life. Like I'm actually there sitting front seat in the theatre. Now the soundstage on the XBA-A2's are not the best I've heard especially from the 300-400 dollar (AUD) price range, there are alternatives such as a pair of Sennheiser HD 598 or the AKG Q701 but those are open-back headphones not in-ears. The Shure SE425 IEM's cost about the same as the XBA-A2's and may provide a richer listening experience with classical and jazz of the like but with a weak bass sound, making it not suitable for all genres. However if you can save up an extra 100 bucks and get a pair Sennheiser IE80's then you'll be pleasantly surprised by the incredibly wide and detailed soundstage with enough bass to satisfy the majority of bassheads with good mid-tones and detailed but slightly lacking highs.

Now after a bit of a think I realised why burning in the XBA-A2's enhanced the sound and cleaned the muddy bass and mids. The XBA-A2's use a "Liquid Crystal Polymer" diaphram for the 12mm dynamic drivers and 2 Balanced Armature drivers to prevent sound distortion. The Balanced Armature drivers don't require burn-in due to it's architecture that doesn't require air to produce sound but the crystal-coated 12mm driver requires a burn-in since it's coated in a crystal film. LCP is known to be used in Kevler and thus, the driver may need at least 24-48 hours of burn-in before a proper evaluation.
Having already burnt the A2's in for more than 2 hours, I'm hearing more detail and less muddiness compared to when I first opened them. But the lows at some parts of a song can still overpower the highs a bit, now I don't know if it's because I'm not using an amp but at 32 ohms I may need one to truly bring out the sound on these.

The Sony XBA-A2 is Sony's mid-range IEM of their new XBA range (XBA-1AP, XBA-A2, XBA-A3, XBA-Z5) and for 350 bucks, it's a solid buy for anyone looking for a great-sounding pair of In-Ear Monitors with a boost in bass making them suitable for most genres from classical to rock to electronic."