There's no point watching the dub after Battle Frontier when TPCi takes over. It's not just the voices that are terrible, it's the actual dialogue (you can tell they're trying to make jokes like 4kids but they're all lame) and how they replace 90% of the background music with their stock violin music.
One example is Dawn (Hikari) getting lost in the first episode of D/P and her theme is playing, making it a light-hearted scene. In the dub, TPCi replaces her theme with some anxiety music and makes the scene look serious for no reason.
Another example is one of Serena's greatest moments, RUINED with terrible music:
https://www.youtube.com/watch?v=shwqP27n81A 
