Interconnect priority

I can't vouch for the validity of it, but people who know more than I do about about audio say the DAC to Preamp is more important, because it's the smaller signal and any deficiency in the signal will just be amplified the further down the chain it goes

What about Streamer to DAC (assuming they're separates)? Further up the chain, more consequential, perhaps?

DAC to preamp made the most significant difference in my system. What is lost at the source can't be gained further down the line. 

When I used Transparent Audio cables a few years ago, their hierarchy was source to pre most important, then speaker cables, then pre to amp...

Agree with all the above — closer to the source is more important.