For those of you who did not know Aqua's voice actor in Japanese is Megumi Toyoguchi. Seeing as she played Paine in Final Fantasy X-2, and Kingdom Hearts II (gullwings), in the Japanese versions the English voice actor probably will be Gwendoline Yeo (Paine's english voice actor) assuming it comes to US/ EU.
-I'm fine with her doing Aqua as long as she doesn't deepen her voice like she did with Paine, what do you think?.-
if you want to see what she sounds like, go to the url below
http://www.youtube.com/watch?v=tY5jwmvfCIM&feature=PlayList&p=D14A768529D4B448&playnext=1&index=46
here's another source
http://kingdomhearts.wikia.com/wiki/Aqua