I went with the one box option, a Cary DMS-700. I tend to keep audio equipment about 20 years, so it IS my forever streamer/DAC at my age. It’s over your budget but worth considering if you can get to $6K, and you’ll save the cost of an extra cable. I believe there’s a used one for $5K on Audiogon right now. And it is a R2R DAC.
From Cary:
While the DAC is made by AKM as it was in previous generations players, in DMS-700 Cary Audio uses not a Delta-Sigma bitstream chip but a R2R (ladder) DAC. R2R architecture is tricky to implement so we designed a ‘support’ code-based DAC extension, programmed in a FPGA chip.