Thanks... I know that the amp section won't be exceptional but it must be at least acceptable within the price range. And that's what I am not very sure with UD-501 especially.
Btw, is it possible to go balanced with HD800 using two pre-out 3-pin XLR connectors (for example at the back section of Emotiva XDA2), or do I need to use "headphone out XLR connectors" (for example on the Sennheiser HDVD800) for optimal SQ?
There's always DIY and this: http://www.bottlehead.com/
The only thing I can think about the XLR out put of the Emotiva is that they're males and most headphone outputs are female. So you're have to get the cable made with female XLRs