[...] a molex and the molex allows 3 power choices been a while since I did that but I think the correct wiring to a molex will yield 9 volts which should still let that fan pull tons of air.
by splicing into a molex you can do 12v, 5v, and 7v. the 7v is by splicing into the 12 and 5v lines (12-5=7).