I just got the XBA-A3's about 2 weeks back while in Japan. I listened to them against pretty much most things and they fit my preferences the best. I didn't try the Dunu's though so I can't give you a perfect comparison. Also I listen out of a rMBP, iPhone 5s or Note7.
The XBA-A3's have an awesome low end, like the XB90EX in quantity and extension at least, maybe less in impact, but not bloated into the mids at all and very quick. The sub-bass extends very deep and is very impactful, you can feel it in your body when it's loud enough, which is perfect for a basshead like me. The mids to me sound just a little dark but not much, but they're brighter than the XBA-Z5 according to me and Lachlan here.
http://www.lachlanlikesathing.com/2015/01/thoughts-on-sony-xba-z5-vs-xba-a3.html
I find that the high end is pretty bright and it helps the mids. But the XBA-A2's were more airy and had a louder treble which opened them up a lot, but the treble was too much it ended up hurting at same comfortable listening levels for A3's. But A2's had a more loud bass section to me, but was slower and more flabby.
They're kinda big though, and get tiring to wear after a while at least for me. They rest on the bottom portion of my ear and end up hurting after a while, but YMMV. They come with a lot of tips and a nice carrying case but the case is a little small, you have to bend the ear glides every time you put them in the case. Comes with a free extra like remote cable but I'm not sure what it supports. Nice IEM's for the price and I liked them better than everything I tried other than the Z5's and STAX 3170's haha.
