spend on the streamer or on the DAC ?

I think this depends a lot on the DAC and how it is connected to the streamer. The Node 2i, for example, only has SPDIF and TOSLINK outputs. A DAC that derives its sample clock from these digital inputs will have SQ much more influenced by the quality of the streamer.

If you are using a DAC that buffers the data and generates it's own internal clock, then the SQ will be less impacted by the streamer. That's not to say there won't be a difference, but I think the differences will be more subtle.

For example, I noticed a bigger difference between my Node 2i and my Bryston BDP-2 streamers which using the Yggdrasil (SPDIF from the Node 2i, AES3 from the Bryston) than using my Denafrips Terminator DAC using the same input connectors. The Terminator buffers and reclocks the data using its internal clock and is much less sensitive to which input is being used (including USB). 

@lalitk

brooklyn bridge
zen mini mk3 with lpsu
aries g1

see my post w list of outboard dacs in this thread
https://forum.audiogon.com/discussions/thinking-about-getting-a-r2r-dac

Invest in the DAC. I've used streamers from a raspberry pi4 to Node2i,  Bel Canto, Simaudio, Aurrender and there isn't a nickel worth of difference between them. If you want to stick with digital input use the Node if you want USB get a raspberry pi4 and get the best DAC you can afford. 

@olica the DAC will have a much larger impact on the sound character, regardless of where it is getting its audio data from. Changing the data source into that DAC will not be able to significantly change that character, and is instead probably best thought of as optimizing for it.

There are also plenty of streamer/DACs built into one unit, like the Bryston BDA-3.14.  Sometimes eliminating two sockets, one cable, and everything that goes along with that, pays dividends.