The Driver X's had one really soft season--09/10 I believe--before they started to stiffen them back up. I own the years before and after 09/10, and they're both pretty stiff. Burton also brought the plastic tongue stiffener back in 10/11, but I find that it crushes my in-step, so it probably won't help you either.
Otherwise, I used to ride the K2 T1 single boas. I was satisfied with their stiffness, but couldn't compare them directly to the Drivers from memory. I will say that the toebox in them felt really short and the footbed felt overly firm. I think I had in-step issues in them as well, come to think of it.
Tried Malamutes and wasn't impressed. My Driver's are stiffer. Also owned Northwave Decades and they were reasonable good.
Interested to hear others' thoughts too. I have some old stock Deeluxe GTI that I plan to break into next.
"''planter ben red' can be put very simply into ''the board stopped freakin fast kinda on its own''--Bomber-member Pat