Which is the best upgrade for the money for steaming from lap to through amp?

Friend

MacBook Pro’s already have outstanding power supplies that include great power conditioning - which contributes to their stellar performance.

Your best bang for the Money would be a good Digital USB cable.   If your budget is limited visit Best Buy and get the  Audioquest Carbon; if not - look at the Wireworld Platinum Starlight 7USB 2.0 or the newer Starlight 8 USB 3.1.

McIntosh equipment is also stellar; so you are almost there as far as Sonics go.

Very helpful.  Thank you.  Be well!    

Have you considered a USB to S/PDIF converter?

I use an old Macbook Pro, with Halide Bridge (USB to S/PDIF converter) to DAC.
All in one cabling is an advantage for me.
Also have an iFi USB Silencer.
At work have a M2Tech Hiface2, which was recommended to me.

I'm considering upgrading the Halide Bridge. It's limited to 24/96.
Although I have no 24/192 at present.
Also have

Have heard people talk very highly of Black Cat Silverstar Coax cable.

See if you can hear a difference if the Mac is on battery or not. If you do, you may need a replacement PS. If you can't, you are good. The real issue is ground loops and RF/EMI noise being caused by the PS.

Thanks for the input... that's something to consider as well which i hadn't considered. Best!