@bosssound Hi, First let me say that the UD-701 is a beautiful looking unit and I was considering upgrading my UD-503 headphone amp to it but then the AKM chip plant burnt down and TEAC had to re-think their plans. They were going to use the AKM chips and I think a few early models had them, but now are using 2 Delta Sigma chips developed by TEAC, clear as mud.
I would certainly go with an Aurender either with or without DAC. They are fabulous machines. I have thoroughly enjoyed my UD-503 headphone amp and used it in a full system and I'm sure the UD-701 will be very good but Aurender are in a different league.
If you are considering a separate DAC you can't do better than the Musetec 005, read the thread on here.