I would avoid ebay coilovers like the plague.
Tien do superstreets for the focus,
http://www.tein.co.uk/
Bilstiens can be sourced through
http://www.european-parts.net/
You'll probably be looking at $1300-1500 for a decent set of coilies. Probably want to steer away from race struts, and look for street ones. They will be softer... I had 10kg/12kg's on my drift car, was unbelievably good on the track, but unbelievably sh!thouse on the road lol.
You'll also need adjustable camber arms for the rear, ~$200 through various places (ebay ones probably wont be too bad).
Also replace ALL your bushes with Nolathane. You'll also want a 24mm swaybar.
Thats getting close to a total conversion, and would make the car pretty hardcore.
Another good way to improve (any car) is underbody bracing. Theres a crowd in Thailand I think called CTECHtuners that do 4-point front and rear braces, as well as fender braces, strut braces, etc. Bracing your car = free horsepower (essentially).
You'll be surprised how hard a 100kw car can go if its stiff as a two day old corpse.
I may have gotten a little carried away there, but the point is don't buy china coilovers!!!