You can go AFE Dry filters if your afraid of the "oiling issue."
afe air filter
Wix air filters?
HKS is also worth a try, they cost a little less than the K & N's. Paper filters likes WIX are pretty much the same as OEM. I would just stick with the OEM Nissan filters if you want to go that route.
Like I said, nothing wrong with going with the K&N's. The Stillen Gen 3's use cone type K&N's.