Icon 2 and Icon uDAC-2 are two different products. Icon 2 is a DAC/integrated amp/headphone amp combo targeted toward full size speakers. The Icon uDAC-2 is a DAC/headphone amp combo. If we're discussing the Icon uDAC-2, then yes, the RCAs are outputs. If we're discussing the Icon 2, the RCAs are inputs. 
The DAC section of the HDP for the money is pretty good. I did, however, find that it has its best synergy with the built in headphone amp (but I suppose that would be expected). Then again, the only separate headphone amp I've tried it with is Little Dot MKIII, and I didn't think it was the best match. That said, I think the amp and phones you're using it with will ultimately decide your end result...
Edited by johnzz4 - 12/1/11 at 8:32pm