An update... I've been doing resarch and it seems that Quaiffe doesn't actually produce any gears for the Impreza yet... I understand they advertise a part, and then wait for customer responses to determine if it's worth their while to make them. Soooooo, until I actually see a set myself, Quaiffe gears are vaporware AFAIC.
That said, I also talked to Paul Guard, purveyor of Porsche gears, and he believes he can turn out gearsets of any ratio you desire, as strong as or stronger than MRT gears, and cost competitive. Have to wait and see what develops there.