Yeah, Chez Ashtons is pretty good poutine, their cheese is great (very squeaky), but I don't think they have the best fries (they just have fast food fries like mcdonalds).
I actually really liked the poutine from le belle province, they had good fries and good gravy. If you want quantity, Green Stop in Montreal has a nice big grosse poutine, but the largest has to be from le roy jucep (think it was in drummondville, stopped there on my way down from quebec city with my wife, it was called the Mega Poutine, they claim to be the inventor of Poutine, but I'm not sure about that). It was like a turkey platter of poutine, it was good, but the sauce was maybe a little too sweet. I just had to order it so I could say I tried, but I didn't even make a dent in it.
My wife thinks poutine is ok, but she's mostly addicted to the smoked meat sandwhiches (she keeps trying to find something similar here, and they have a smoked pastrami at a deli here that is close, but not quite). I miss quebec.