Just go the little beastie from China, complete with a balanced jumper. I have only had enough time for first impressions of the DB2 with the PB2, using Grado SR225i and Senn HD650 phones (the later balanced).
I compared to my reference Sugden CD/Preamp system output - the DB2 took a digital feed from the CD player and played via balanced cable into the PB2. My reference system is still the best, just. Even its single ended configuration has an authority and ambience over the DB2/PB2. (Christy Baron CD). The most notable difference was a slightly leaner presentation with the iBasso system. The difference is getting slim though and probably down to the decoupling capacitors. (I have a feeling that the Sugden is DC coupled)
I then compared an iPod Gen 5, via Kimber dock cable - single ended and the same audio file, via SPDIF from the iMac, through the DB2.
From worse to best: (using SR225i's - single ended - since they are very revealing)
iPod 5.5 - dock single ended output - reasonable ambience, frequency extremes not particularly well defined, certainly in the bass. Reasonable presence and ambience.
iMac - DB2 -via SPDIF, single ended coupling int PB2 - much better bass definition, could hear the double bass being plucked and pick up subtle undertones. Tighter transients and considerably better presence and ambience around the vocals
iMac - DB2 - balanced coupling to PB2 - about half the improvement again - in the same areas too - better and deeper bass control - further clarity and presence. Seems slightly sharper too. I was veering towards ditching the SR225i's but the DB2/PB2 combination has improved the overall balance in a most alluring way.
I guess the DB2 has caps in there , so I had better do a burn-in and repeat this next week sometime. Once the burn-in is complete, I will also wheel out the HD650's so that I can find out just how better the bass is.