Definitely upgrade the DC-1. My Emotiva DC-1 doesn't really respond to better transports like the BDP-1, such as my other DACs. What about getting a used BDP-1 and BDA-2?
I know the BDP-pi is supposed to be faster than BDP-1 and BDP-1 USB, but in terms of sound without having a linear power supply built in and all that other stuff...I could be wrong here, but that's my thinking. If I get another BDP for a system, it will either be another BDP-1, or the BDP-2...I don't see the use for BDP-pi, unless convenience is the most important.