I'm guessing Nancy Cartwright (i knew her name
) also does Nelson Muntz. Can't be bothered to click the link.
The voices are not enhanced, as before 1992 or 1993 Homer (who's voice is done by some bloke) was supposed to sound a bit like some famous American bloke who was a bit of a dunce. But then they changed it to its present state.
Marge's voice has developed more, from a croak to more of a sort of female mafia person
Maggies i don't notice much difference
Bart is much the same, but once more his is more developed from his original, which was very sort of Gullible and stupid.
Lisa sounded alot younger, more like a normal 8yr old when the program started, now she sounds like a woman, but with an undeveloped voice. I don't like her voice now, especially when her and Homer go into those tanks at the weirdo hippy lady shop.
(not addicted to the simpsons!)