If you want more power id go zetec tbh, thats what ive done. Keep checking all the sites and a good engine will turn up at a reasonable price. Ive bought a zecond hand zt that was in a 400+bhp mk3 fiesta built by devil developments at a fairly good price.
I'm only planning to run around 300bhp as that'll be plenty in a mk2 fiesta but bottom end is capable of 500bhp!

Grant