There's no one 'best; plug. I prefer Iridium plugs (NGK) as well - though not because of any perceived 'performance' boost (there really isn't one) but because of the run-time between changes. You don't have to pull them out as often to change. You won't get noticeably better economy or performance.
Also, if you don't want to pay $12 or $15 or more per plug, then get them off Amazon.
I have Iridium plugs in all my vehicles (04 Envoy, 90 Isuzu pickup, 06 Burgman 650, but the Genesis comes standard with them).