Hello, I wanted to share my experience with my UE900 for about one year of customization and use.
I'm happy to say that there are no connectors issues with mine.
For the SQ, the cable provided are ok. But the sound seems to be 'blurred'. The soundstage is great and spherical, but the instrument placement a bit off for me (a bit abstract). It still fun, but the comfort is no good around the hear.
I wanted to experiment with different aftermarket cables, even custom 'silver+copper hybrid' one (For a cost, but great). Which sound great with a lot of details and separation, with good bass but I'm using my UE900 for commuting so I needed a fun sound. These cables are OK for analytic listening like classical, jazz. And the cable was a bit big too and the tips were always seems to getting outside my hear. Still the sound has bring clarity never found in the black or blue cable. It seems that aftermarket cable changes the sound greatly. It can brings more bass, clarity depending on the metal used for the cable.
The Fiio Cable is comfortable but as a lot of microphonic. It as a lot of details but no low bass. Good for certain genre. The soundstage is a bit congested too.
My latest cable is this one: http://www.ebay.ca/itm/261228539161?var=560205145976&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 No microphonic at all and comfortable. Great clartiy, highs and profound bass. The soundstage and separation are not like the hybrid cable, but still more focused, a bit more intimate (closer to the head). Not that expensive like other custom cables out there too.
I've tried blocking the small bore on the nozzle, but I still wanted a bit of fun with my bass. (the rumble)
Also I found out that the sound from my Iphone was a bit boring. Using 320 mp3 was not enough. Tried amping my Iphone but it was too big and I wanted to make phone calls too! ;)
So I bought the DX-50 wich is fantastic and upgraded all my music to FLAC. I am happy that the UE900 are high impedance and that the DX-50 seems to like it as well. The pairing is excellent. Still im switching between firmware to get the best sound. 1.2.2 and 1.2.3 for now. :) No amp for me because I don't want a big brick in my pocket! Portability please.
About tips, it's been almost a year that I roll between tips to get the most comfort and isolation. The provided tips are OK, but I don't know if it's my ear canal, I always felt that they were not well in place. Tried different Complys and It was the same: never get the proper fixed seal. Tried double flange: fail.
So I've looked at different threads of people experimenting with different tips with other iem. Customs made Universals one.
Bought recently the Ortofon replacement tips and they are long enough for the stem of the IEM and I get superior seal and a feel that they are firmly in place. And they are comfortable too! Hurray! (For a cost, but worth it)
Hope that my experience help UE900 users!
Next step: CIEM in a couple of years.