Have you forgotten about vertex shaders? What are the vertex shaders on those cards? If the GTO is somehow drastically higher, then go for that. Though I doubt it. Doesn't hurt to check, though.
EDIT: Oops, didn't see the other pages. My bad. Don't know if y'all have come to a conclusion yet or not, so I'll leave that there.
EDIT: Oops, didn't see the other pages. My bad. Don't know if y'all have come to a conclusion yet or not, so I'll leave that there.