They dropped dubs some years ago, Atelier Firis (the next game after Sophie) is the last one to have English voices.

Earlier games (especially the Arland subseries) had pretty decent dubs, but Sophie's and Firis's dubs are only partial, meaning most scenes are unvoiced. For this reason I'd recommend sticking with Japanese voices. Not to mention that if you ever decide to play Sophie 2 or Lydie & Suelle you'll have to get used to Sophie and other returning characters' Japanese voices, which might be a jarring transition.