You can only buy them in a 3 or 5 pack from PCS. Also the LL additional fans are RGB, where as the standard case fans are not.Wouldn't it be better to get two fans then?
That way there would be 3 intake fans and 3 extraction fans, but since 2 are powerful liquid cooler fans, there would still be more extraction than intake?
The extraction being higher than intake, will allow better cooling for your GPU. I had GPU temp issues at first with an elite capellix, where my gpu was sitting at 80 degrees, which puts the gpu fans to 100%, so i kept the intake (elite capellix ML120) on quiet and exhausts (ML120) on extreme and the temps dropped 12 degrees, whilst the pc remained near enough silent (sub 30db).