For a TV show originally broadcast in SD and early HD, a 1080p release from a source like a Blu-ray or a high-quality WEB-DL (web download) represents the highest possible quality for most modern displays. It's the definitive way to watch the show.

If you are looking to optimize your own media collection, let me know:

"It's an illusion, Dave," Kevin corrected, his eyes fixed on the screen. "And you’re seeing it in ten-bit depth. Look at the contrast ratios."

for the first, second, and third seasons.