Your music is likely going through several transformations:
- Digital music file
- Converted to analog sound wave (music player on laptop)
- Converted back to digital signal (Bluetooth encoder)
- Converted back to analog sound wave (Bluetooth decoder)
- Turned into physical sound waves (Headset/speaker system)
The YMB is performing step #4. Each step introduces audio quality degradation.
For maximum audio quality, some Bluetooth A2DP receivers understand more codecs besides the single, required SBC codec. This can eliminate steps 2 and 3.
Also my guess is the Bluetooth SBC codec does not have the best audio quality. Ideally, the audio codec used should be lossless, but even lossy codecs like MP3 can sound acceptable. I am not sure if any Bluetooth products that support lossless audio have been released.
Finally, the other stages of the list above must all understand the Bluetooth protocol properly (music player, bluetooth encoder).
So, to answer your question: find a Bluetooth receiver that understands a better codec than SBC (ideally lossless). Make sure the rest of your Bluetooth "stack" also understands the same, better codecs.
More info: Advanced Audio Distribution Profile#Support of Codecs
Update: As I said, a lossless Bluetooth audio solution may not be availalbe (I've found a lot of announcements, but no actual products) but it may also be overkill unless you're a serious audiophile. Simply using a non-SBC codec may be enough, but few products are marketed with those technical details.
You may get a lot of returns simply by ensuring that your YMB and A2DP source are using a non-SBC codec. (The (software) Bluetooth encoder on your laptop may simply not support the proper codec. I'd check into this, since you said your other sources sounded acceptable. Your results may vary with the type of audio file you are playing!)
Also, I considered alternatives to Bluetooth A2DP like wireless audio via 802.11. One such solution is the Apple Airport Express with Airtunes. (Plus software for non-iTunes/Apple applications.)