Your OEM sparkplugs is already very good. If you want aftermarket brands then consider the ones made by Bosch (Super 4, Platinum) and Splitfire. Goodluck.
woooo.... P700+ kamo ang isa ng bosch platinum? makakabili ako ng 10 stock plugs for just 1 bosch platinum, meaning meron akong 40 stock plugs for my corolla gli... hehehehe kahit every year na lang ako magpapalit ng spark plugs that's 10 years equivalent. labor? kayang kaya diy ang spark plugs.
Use stock sparkplugs. Fancy & expensive sparkplugs wouldn't add to your performance. Other sparkplugs last a very long time and worth the investment though. Like torquemaster.