From previous experience it will not help at all.
Back before BitCoin mining was cool, I have run a few quad crossfire setups. The first one burned because I had a single fan running off that molex port (obviously the PSU was connected to it too) ... and the small amount it drained was enough to tip the scales and the main socket burnt.
How could you possibly be running a fan off that molex port?
The molex port provides power INTO the motherboard, not out.
Those molex slots help a lot in my experience. Got one running 5x GPUs without the need of a powered riser. Been rock solid for 2 yrs.
On the other hand, another board with 4 cards burned up within weeks.