I've listened to a lot of aptX and SBC, and I'd be very surprised if most people would be able to tell the difference on good source material. From
Hydrogen Audio, this cherry-picked quote on SBC: "SBC can use up to 372 kbps if you are lucky.
So if you don't want to have lossy to lossy recompression you will have to use FLAC or not Bluetooth. AptX will recompress too." From
WikiPedia, aptX has a bitrate of 384 kbps. I've done volume matched comparisons of aptX and well-implemented SBC, and I'd be hard pressed to tell the difference between them. The limitation in most bluetooth chains is the DAC and amplifier built into the headphones, not the codec used. By using wired headphones with the M2s, you avoid the amp and DAC problem. I would challenge anyone to do volume matched comparisons of aptX and SBC, if you can consistently hear the difference I'd love to know your methods and give you a high five for having amazing ears. In double-blind ABX tests people have struggled to identify CD versus 320kbps mp3, this is an even smaller difference. I don't know if aptX-HD sounds better than SBC, as I haven't checked it out, but all of these solutions are lossy. There is apparently an aptX lossless codec, but I've never seen it on a device.
Long story short: well-implemented SBC isn't much different sounding than aptX. Chances are differences you are hearing are due to amplification and DAC differences, not the codec. People shouldn't be afraid to use HiBy connect with the M2s, it works and sounds great.