spend on the streamer or on the DAC ?

DAC

Dac (no question)

OP: From all the above posts, and is fairly well agreed on by many:
1) The Streamer is not more important than the DAC. It could be just as important in some cases but usually less important.   More often the DAC is more important so focus on that first.
2) Given that you are striving to use high end components, the 'Synergy' of the component chain, input, output connectivity and power handling will often be more important than any of the individual pieces - and if you want to get good value, then finding the right blend often requires a lot of educated guessing, and trial and error.  See if you can buy with a good test and return policy.
Best Regards

They’re both really important.  I recently upgraded from a Mac Mini to a Lumin U1 Mini and the improvement was massive in my system.

That said, I would start with the best DAC you can afford and plan to add a streamer as your next upgrade since you can stream from your MacBook.

yes indeed

going from a jittery noisy everyday computer, not optimized for music streaming, to a dedicated streamer will see a huge improvement in SQ

but going from one decent dedicated music streamer to another, not so much, usually

ymmv as always