The E1 really is an amp/dac by itself. It has a lot of potential (especially when swapping opamps) and it's not that expensive over some other dacs/amps.
As Linus already mentioned, please visit us over on head-fi.org and we will be more than happy to help you out!
http://www.head-fi.org/t/542563/asus...0#post_9149457