17% in T^4 is almost 2x - plugging 293 (in Kelvin of course) in the calculator i get 417 W/m2 vs. 784W/m2 that i got earlier for the 343 (Kelvin for the 70 Celsius).
The ISS targets rejecting 70KW and has something like 140m2 of radiators. These radiators are attached to the ISS and use a lot of plumbing to carry the cooling liquid.
Where is GPUs and everything can be attached directly to the radiators and solar panels. So 70KW - 70 GPUs - can be placed right onto the 10m by 10m radiator panel. In front of those GPUs sitting on that radiator - a 15m by 20m solar panels assembly. Whole thing is less than 1 ton. Between $10K and $100K on Starship.