Got mine today... Japan-market via eBay, 1002625. No bass issues.
Sounds roughly similar to my NW-WM1AM2 in the bass department, definitely the same familial DNA. Perhaps the bass is slightly faster and punchier and slightly less sub-bass focused, but from what I understand, those are the differences one should be hearing between the two machines, when both are performing as expected. This particular NW-A306 is certainly not bass-lite, in any event.
HOWEVER... There are a few other issues:
-Overall bugginess in the Android OS. There can be a lot of lag both in and out of apps. Certainly not the upgraded experience to the 1AM2 I was hoping for. It's markedly worse in this department.
-Initially it said it couldn't connect to my WiFi, and when I backed out of that screen it read as connected.
-Early on, when I was in the middle of getting started with the device, the screen went black and ran me through the whole initial setup process again (wifi, signing into google account), despite the fact I had already done all that, and was in the middle of downloading Apple Music.
-Just now, when I started it up, it stayed on the black "Sony" screen and didn't progress to the "for music lovers" nor the home screen, and I had to restart it.
-Low but audible static feedback when Wifi is on... the device seems to be acting as a radio receiver and picking up stray signals. Luckily, I can't replicate the issue (so far) when listening offline, so this last thing doesn't bug me so much... I only listen to downloaded music.
In any event, it sounds great when it's just playing, so I have hope either a reset or a firmware update will correct the bugs. I'll update you all if I decide to do the reset. I'm a little afraid of the correcting the bugs and picking up the bass issue, lol.