For me, still wait and see the end of the fight to understand Suzaku's real might. This fight can only be stated in Round 1 currently as we haven't seen Suzaku's climax level.
Selene, without being serious, could be Eileen's level who pushed back, while hidding her DS's magic nature, an amusing Acnologia who was impressed until asking her name. For me, actually, I put both Suzaku and Eileen close in level, as they resist well against amusing allmighties foes portrayed around equals (still put Acnologia slightly above DG until now).
Eileen can cast enchants in same way Selene used in first round against Suzaku, and Suzaku can slash through like he did. Both need to get serious (Round 2). And we still don't know Suzaku's real strength for now. Selene and Eileen are close in mind : arrogant, allmighty, some psychotic when they are push to get serious. A fight between these two (Eileen vs Suzaku) can be the same scenario as the one in chapter 81. The difference, I think, is that Selene must have more hidden power in reserve than Eileen, just like Acnologia had.
For me, they are currently match. If Suzaku can do something against a serious Selene, I will give him my vote. If he won't resist anymore, I will stay in Eileen's matching level, which is, for me, on top of the Manga (in that way, Suzaku did well and he has nothing else to prove even if he falls soon).
My vote should be more precise vs August who can't use his hax to Copy Magic without tool. August is strong even without his speciality, but I think Suzaku can put a win against him.