If y'all don't imagine Fergus, Downey, Matilda, or Goldie with those voices (or even Don Messick, June Foray, and Joan Gerber as Fergus, Downey, and Goldie), what other voices do you imagine them with?
Quackmore's gotta sound just like Donald, right? That's always how I've read his voice. I've always read Donald's voice in Clarence Nash's and/or Tony Anselmo's voice for him in the cartoons, so that's what I hear for Quackmore, too. No strong opinions on the others. Downy definitely has an Irish accent, though.
No matter what I say or do, know that Jesus loves you.