I think there are a handful all motor hondas running 300+ whp. Slap that in a gutted car like a CRX that would only weigh 1800lbs or less, and yeah you'll have an EVO killer. But Those motors are built to the hilt - super high compression, oversized valves, ridiculous cam grinds, blueprinted/balanced bottom end, dyno tuned standalone, maybe ITB's, etc. You can turn 9K+ RPM out of them.
But you're also talking an EASY $10,000 into the motor... you can put half that into a nice turbo setup and make twice the power much more reliably...
There's been a whole bunch of Escort/Protege guys that have built all motor BP's - they breathe so much better than the anemic B6. I think they've put down 180whp or better with ITBs, but it's been a while since I looked. I am building ITB sets that would fit the B6 though, so I may attempt it someday for shits 'n giggles, but the BP is where you will make much more serious power - both N/A & turbo.
Also, you'd wanna ditch the n/a Ftype transmission pretty quickly
My 2¢
-Rocket