Aren't the smaller lowering springs usually stiffer to avoid bottoming out under normal driving conditions? The new springs might not sag as much as the old ones comparatively.
Why not go with a SAZ-1000d. I think they are cheaper, and it's 1 ohm stable. I don't think the rockford is, but I could be wrong.
BTW, I meant cheaper then the rockford. The Audioque amp would be a good choice as well.
I would guess no. It looks to me like its meant more of small circuit boards with that probe and ground clip. But I don't really know anything about oscopes.