Instead of those Expensive Fans, Why don't you go toi the Auto Wreckers and pick up some old fans. Up Here I can buy GOOD Used Fans for about $10.00. Other than looks, I doubt those Performance fans are much better.
Before going any Farther, Check the Battery Voltage, With the car Running at a reasonable RPM. It should Not Exceed 14.5 Volts. If it does you have a regulator problem and a definate cause for failure of the fan.
Also, Instead of using a Relay, why not use a Mosfet to Sink the negative lead of the fan to ground. Less Chance of Relay Chatter, or Contact Resistance Problems which may Cause Excessive Current.
As to Amperage or Current, Both are Totally correct and I can easly understand a Manufacturer using Either Term.
I do Agree that Excessive Current Usually Requires Higher Voltage. But Also by Too Much Drag on the motor, caused by the Fan, or possibly a Problem with the Relay as above.
Hope this Helps.......Gary