A fine list. You don’t really have to stack the Zen CAN with the Zen DAC. They’re an aesthetic match and have the ability to connect to each other balanced, but it’s not essential to pair them. Any budget dac should be fine for the CAN amp. The Zen DAC does have a pretty strong price/performance ratio though. You will also sacrifice optical and coaxial digital inputs, if that matters to you.
As far as DT880 balanced modding, we have a whole thread for that:
Let us know how it all turns out and enjoy!