Looked at the iFi power modules and they have one that does 5VDC@2.5Amps that will run a RPi3. It also comes with the micro USB power connector.
Have tried Moode Audio with the RPi3 and it works, but has some volume control problems with the Meridian Explorer2. I believe that has been solved with the latest 2.6 release, so going to give it a try.
Since the Amanero asynchronous USB to I2S Bus converter is here from another DAC project, bought one of the AK4490EQ DAC board from Ebay for $28 shipped. I already have the 25.2VAC CT E-I core transformer and dual 9VAC Toroidal transformers, so just connected them up.
Working on the cable harness for the I2S Bus and DSD interfaces to see what it can do. Supports up to DXD and DSD256 rates for incoming data. Board has RCA outputs to run my iFi iCan headphone amp. Should be an interesting setup for portable use.
In this case the entire music server/HiRez DAC setup is about $250.