I will say that I am impressed with the Horizon series 12AU7. I was NOT expecting them to sound this good.
I purchased this set to save my NOS Mazdas. The Mazdas are amazing, but these are so good that I don't care about doing a comparison. I am in no rush to put the Mazdas back in the system and can rest easy that if something happens to these Psvanes, I have the Mazdas to go back to. I will say that they are indeed neutral compared to the ART series. In the initial hour, the bass seems a bit muted, but has opened up since. In fact I feel that the bass is more taut. And they do glow a bit from bottom up. Very pleasant when you look at them. The Mazdas glow very faintly compared to these Psvanes.
The biggest concern for me is - how long will these last. Keeping my fingers crossed.