I have a little experience with this. I own both the Denefrips Ares and the Holo Audio May Level II. The May is significantly better, though it is also significantly more expensive. Whether you want to pay the extra freight is a value judgment you'll have to make. My guess is that the Pontus outperforms the Ares but I don't imagine it is by a significant margin, but the Pontis would be a reasonable choice.
I have no experience with the other models.
I have no experience with the other models.