So, I have a question about soft/stiff spiders vs more or less power.

[Krakin]

Progressive spiders get stiffer the further they travel. Linear spiders retain the same stiffness as they travel.

I think you said that backwards.

A progressive roll spider is designed to keep the stiffness of the suspension as constant as it can throughout the coil's motion. The further the coil moves, the more useful it is, so they are more common in longer-throw subwoofers. It is still useful, though, in virtually any speaker that seeks more "clean" throw than other speakers of a similar size.