In my random cruising around the net, I've found that no, an impreza suspension is not the same as a crosstrek, so swapping over will lead to failure. I came across RS-R springs from a post that appears to be the poster car for the company, but it looked like exactly what I wanted. Not garbage coilovers, not slammed, not wrong setup for a different car. So I ordered a set and the UPS guy dropped them off today.
According to RS-R (who calls them "good handling springs), it drops front and rear 1.2". The rear springs are progressive. I took the car for a ride on twisty back roads to try them out and I'm quite happy with it. Not slammed like some 16 year old's car and not a bouncy, Honda-esque chinese coilover garbage.