I've spent time in Imprezzas, and while they definitely have their strengths, you might be pleasantly surprised in a Forte.
The handling isn't that far off between the two (especially if you go for a Forte SX). In fact, the SX has a very firm, but well-controlled ride--definitely firmer than the stock Imprezza. The SX has decent power (and indecently decent torque), so I doubt you'd be disappointed there, either.
I personally MUCH prefer the Forte interior to the Sube's; higher-quality materials, much better design. I'd rate the Koup SX's seats as considerably more supportive than the stock Imprezza seats. And the Forte is considerably quieter, too, though all bets are off on that if you mod the intake or exhaust
You'd be saving money on a car that you just might wind up liking as much as your Sube. Try to get one out on a good, long test drive and see if you agree.