I may as well tell you now that there is a charisma bug in SoA/ToB if you can be bothered to exploit it.
This allows you to wrap any charisma around to 25.
I wont give you the details of HOW to do it, you can have more fun finding that one out for yourself.
This means that:
(5*18) + 3 (Charisma stat) = 93 points
Are all you need for a perfect character.
After going through Baldurs Gate, you should have:
STR 19
CON 19
DEX 19
WIS 21
INT 19
CHA 4
Well, depending upon your race. Like I said, CHA will wrap around to 25 if you do things a certain way... giving you an INCREDIBLY powerful character.
Anyway, this was just a mild introduction to powergaming. Prizes for guessing the best class to start as