Rand, level ++1 and Nynaeve level 4 +Choeden Kal

Cadsuane, level 5 (9) + angreal (made her ++1 according to the Companion)

Merise, level 14 and Narishma (possibly level 14) and Elza, level 25 plus Callandor ...

Battles:

Verin, level 17, Kumira level 24 and Shalon (minimum level 16) plus weak angreal

Faced Graendal, level 3 + weak angreal (pushed her to "male levels" ++3?)

Alivia, level 1 plus ring and bracelets = 2-3x ++1??

Faced Cyndane, level 2

Daigain, level 45, Eben (unknown), Beldeine, level 16, Nesune, level 15

Faced Aran'gar, level ++3

Flinn (unknown), Corele, level 18, Saren, level 18,

Faced Demandred, level ++2

I'd guess from these circles that Flinn is considerably stronger than Eben was since they faced a stronger and seemingly more skilled opponent and came off better than Eben's circle. I would say it's safe to place Flinn, as a minimum, in the upper Aes Sedai strength ranges (maybe as high as 15-13). Eben was strong enough to Travel (TPoD), which according to the guide makes his minimum strength 19, but it's doubtful he was much stronger than that since his circle had 4 and included the 2 strongest Aes Sedai aside from those occupied with "air cover" and if he was much stronger than 19 either Nesune or Beldeine would have been relegated to Verin's circle to balance out strength since Cadsuane was almost certainly unaware of Verin's angreal.