I just got offered a deal for 6 brand new ngk iridium IX spark plugs for 36 dollars, would this be worth my while or would i be better off going to napa and buying 6 of ngk's platinum spark plugs that come stock with our max's

 

I bought the same plugs on Ebay and they work fine. I don't think they last as long as platinum but I change my pluga every 20k anyway.