This was, perhaps still is, a widely discussed topic not only on this forum but many forums for different makes and models. From what I've gathered from this site, your safest most conservative route to take is to stick to oem for both the coils and plugs. This may be more costly but sometimes you know a guy.
For coils (cops) check out the Visteon Coils/Cops thread that's current discussing Visteon coils off of eBay. I think I got them quoted at around $60-$75 a piece from the dealer, with the Visteon ones off eBay you'll be saving a boat load of money for parts coming from a company that's owned by Ford.
If you do choose to get them from a dealer, give Maxx a call (first LVC sponsor on the right side of the page) I forgot the discount but he hooks it up he's "the guy" for us people who don't have a guy.