Increase Value 2 in the math node until the light hits what you want it too. I am not sure what the value is (as far as mm, inches, poser units). So it will take some experimenting.

Value 2 is the distance the light travels, and you can bet that things like scaling affect it.

And as far as Poser having a lightfalloff node. Poser does indeed have one. But it is a bit different than the one in Cycles. You can not properly attach it to a lights, because it already is part of it in the background, and it works very oddly on props.... The Smooth function in Superfly works on a miniscule scale compared to what it does in Cycles. 

It would really help if we had a live Cycles preview to see what your doing when messing with settings like these....

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