You can't just say Ebay coilovers...there are a variety for sale on that damned thing. Regardless, stick to known brands and you'll be fine. Skunk2 are ok but tend to run some pretty aggressive spring rates. GC are great IMHO since you can customize your rates, height, diameter, etc. I'd also look at picking up a set of new shocks as your stock shocks will probably not be able to handle the increased rates for very long. At the very least they'll lead to a bouncy ride. Since doing it right requires a shock upgrade you might also want to consider a full threaded body solution such as Tien, Zeal, H&R, etc.

Also, why go with coilovers? Are you going to corner weight the car? Do you need the adjustability? If not, just go with a set of sport springs from Eibach or H&R. It'll be cheaper.