with current developments i would say a blacktop zetec would be best as there seems to be a few people with that now so there is much being learned in terms of tuning them and making that power usable
your biggest problem if you wanna stick with a erst is getting it to be able to use the power- with a new chassis like the focus mk1/2 its hard enough making that power usable i would think- in a 20yr old escort you really will have to go town on it!