Also, not related to 501 vs DAC 200, but when I most recently took in the Weiss 501, I was curious to try it as a headphone amp. I recently got myself a pair of Hifiman HE1000SE, which are not hard to drive, and the 501 has a good reputation as a headphone amp/dac/streamer combo.
In my experience, I much preferred a much less expensive stack - a Topping E70 Velvet R2R DAC and matching Topping L70 Balanced Headphone Amplifier. The Topping stack had better control and more engaging presentation, when hooked up to my MacBook Air’s Roon / HQPlayer output in DSD in comparison to the Weiss, which was more refined but not as engaging. The Weiss felt quite passive to me in this configuration. And despite the Topping Stack sounding great with Roon and HQPlayer out of a MacBook with DSD format, it still sounded superior in PCM once I switched the source to an Aurender N200 using coax. So the source component’s quality does matter a heck of a lot here, too.