A few days go I received my Zowie XL2540K, and I gotta say, comparing to XL2546K I'm quite disappointed. XL2540K has pronounced pixel inversion artifacts
(vertical lines appearing on the screen in motion), just like both of the older-gen TNs I tested had these artifacts as well (Omen X25f, XL2546), while XL2546K that I tested had basically none (barely visible from a close look-up). On the other hand, colour accuracy seems to be better on my XL2540K than on XL2546K, contrast ratio also appears to be better (I use a dark scenery location in a particular game to compare).
Now, I don't know what panel XL2540K uses exactly, but I suspect that it's not the same panel that is used in XL2546K. Perhaps I'm super unlucky, but I think it just can't be a coincidence that all other TN monitors that I've had, besides XL2546K, had pixel inversion artifacts issue, so I can say it's a common problem on older-gen TN panels from my own experience, that's why I suspect the panels are not the same in XL2540K and XL2546K. Or perhaps this could be the matter of fine-tuning the panel? I'm pretty sure I've seen Zowie representative posting that XL2546K gets manually fine-tuned by Zowie, especially for their DyAc+ implementation, while XL2540K obviously doesn't. On the other hand, the Zowie representative could only mean that it's just fine-tuned for DyAc+, nothing else.
To sum up, unfortunately I do not recommend XL2540K because of pixel inversion artifacts. I wonder how can anyone use a TN panel with this issue and be ok with it, it's just unacceptable. If 3 out of 4 TN monitors that I've had were affected by this issue, I'm pretty convinced all of them, or most of them older-gen TNs are plagued with these artifacts (Chief also said it's common in TN panels afaik). Mind you, I've also experienced this issue on high refresh rate IPS panels, but never to such extent as on TN ones. My previous unit of VG259QM had some inversion artifacts, the other one was free of it.
By the way, I don't know if someone posted this before here, so just FYI, XL2546K/XL2546K-B and XL2540K/XL2540K-B are exactly the same monitors. I guess "B" only stands for "black" or something. The model ID contains "B" for both models, as seen in the picture I took:
[Moderator note: embedded [img] for convenience ]