By rots, Anakin is at the same level, if not barely below the likes of Mace, Sidious, and Yoda.
Just 5 years after rots (in the novel lots), Anakin/Vader states how his suit strengthened his connection to the force. So I'd say by this time (14bby), Vader is on Mace's level... OWK takes place ANOTHER 5 years after that novel. Another 5 years of growth. I'd say by this point, Vader is a level above Mace, and an amped Kenobi proved to be on Vader's level.
Are there any canon sources that contradict this line of thought?
After giving it some more thought, I think there's some merit to the idea of Amped Kenobi being above Mace. Specifically, when it comes to the Force.
Mace Windu, in his relatively few TCW appearances, has some of the most impressive TK feats in Canon to date. Blasting apart a whole wave of droids, including droideka, with a single Force push, and pushing the AT-TE are both top tier feats that very, very few Canon characters have matched. However, 9BBY Vader hasn't just matched that level of power, he's one-upped it by repeatedly ripping shuttles out of the sky with TK (once in LotS, once in Kenobi).
While I'd put 9BBY Vader and Mace Windu in the same tier as Force wielders, I would say Vader has an edge in pure power. And since Amped Kenobi was demonstrably stronger in the Force than Vader, that would put him above Mace as well. In a purely Force-based contest, Kenobi would have a good shot at winning, with Mace's shatterpoint ability acting as a potential wild card.
In sabers, I still think it's Mace's game. Plenty of statements show that Vader is more powerful than Anakin in the Force, but Vader is also depicted as a less capable duelist than Anakin. Struggling against the likes of Eeth Koth and Cere Junda should be evidence enough of this. What's more, Vader was fighting relatively on par with a RotS-level Obi-Wan, while Anakin was largely dominating their RotS fight and Kenobi spent most of that duel just trying to survive Anakin's onslaught. Meanwhile, Mace held his own against, and even arguably defeated, Darth Sidious. Bear in mind, we've twice seen Vader duel Sidious, and in neither instance did Vader hold an edge over his master.
So, to sum up:
Round 1, Mace
Round 2, Mace
Round 3, maybe Kenobi, but shatterpoint is a wild card
Round 4, Mace