Based on the reviews so far, I gather that the FA-011 require a decent amount of juice to be driven to their full potential. The uDAC-2 and E7 are no doubt very good for the price, but I think you may need something with a little more oomph.
Even at the budget end of things there are plenty of options:
Audio Gd NFB-12
Zero Dac/Amp
Matrix Mini-i
NuForce HDP
Maverick TubeMagic D1
Audio Gd FUN
iBasso D6
Little Dot DAC II
There are plenty more suggestions that I'm sure people will offer.
In terms of synergy, I think anything that can deliver plenty of clean power with lots of headroom, and doesn't impart much of its own signature, should be fine. The Audio Gd stuff has a great rep and offers the best bang-for-buck of any manufacturer. As does the Zero and the Little Dot. The Mini-i has quite a lot of features which push up the price somewhat, so if you are not interested in the LCD display/preamp functionality then it might be worth looking elsewhere. The D1 is excellent, great warm sound signature, only thing is that with the FA-011 the bass might be a little loose and undefined, this is purely speculation based of the reviews so far.
Only you can say whether any one of the combinations has real synergy, it's a good idea to give some of those products a try to make absolutely sure.
Zain
