I wouldn't call the magnecors flash aftermarket, more motorsport quality. I was advised by another member who'd fitted them as I was originally cynical about non OE leads after similar bad past experiences on other cars.
If in doubt, go for OE as the Nissan are good quality..... but technically the magnecor 8mm and 8.5mm are of similar quality utilising OE connectors with better specification leads. My 8mm were £65 inc p&p I don't agree that you shouldn't have decent leads unless you're over 400bhp. Emphasis is on decent though.
Jim