I carry Lumin and have the X1 here, and was just at a client's place last week who has a dCS Vivaldi stack. I'd say the sound character goals of Lumin and dCS are probably best considered as different, so you'd need to hear them to decide which direction best matches what you're looking for.
Lumin X1 or dCS Bartok
Both of these beasts look like they could be that “forever purchase”. These are basically the newest offerings from both well respected companies and are within spitting distance of each other price wise (without the Bartok headphone option installed). Anybody heard both and able to comment?