The 2.0 fixes the low frequency and high frequency extension problems for the Ack (at least in my system).  I however have not heard the E5.  I just took my 1.2d to my friend's, who has a Proceed CDP.  The Proceed CDP I thought was nicer than the Ack 1.2d.  We did not use the same interconnects, though, and I also accidentally reversed the interconnects I brought.  I have the Proceed PMDT, which is a trasport only.  In my system, the Ack Dack 2.0 is better than using the DAC in my Proceed AVP.  Additionally, I've compared the Ack 1.2d versus a Shengya, and like the Ack better.  However, again I used different interconnects.  (I did this so that I could switch back and forth between the two.)  Did you use the same interconnects?