For my knowledge it IS possible to cast Nine level spells in SoA, Just use scrolls or install a Exp. Cap remover (I'm not sure if you cannot cast Nine level mage/sorc. spells without the Exp. remover never played without it so)
here you should find a working Exp. cap remover ---->>>> >>>>
http://www.sorcerers.net/Games/
and if your party consist of 5 party members you will surely be casting nine level spells before entering the nine hells (just do enough quests ect. for the experience
)
the Exp. cap remover removes the barrier Black Isle made for the amount of Experience you can get (leveling) so you do not get overpowerd (like a party of : Sorc. level 34, Beserker level 36 and a Priest level 31) the Exp cap remover will counter that effect by removing the barrier Black isle made.
You can now reach levels up to 40 if you wish.