I have 2 extras, I bought 3 off eBay for $90. Haven't tested them, but the 1 I did replace works... so I am pretty sure the other 2 I bought along with it work also. OEM parts.

 

Which ones off of rockauto should I get? I was thinking Hitachi
By the way I replaced all 6 coils and plugs a couple years ago at 90k with the "replacement" ones made in china. Nissan dealship recently discovered a valve leak with oil on plug 2 and I am having gaskets and covers replaced next week. I figure I should have a few plugs and coils ready to replace them, however I would think having two different types of coils would be bad right?
Also , I can't remember which kind of NGK plugs I used. I think it was platinum or iridium.