Hi,
I've got one 10" fan running on mine so two 8" will be plenty.
You can buy the THERMOSTAT KIT (IN-WATER) direct from kenlow which enables you to completely overide the car thermostat control so it kicks in earlier or later depending on what style of driving your doing.

Buy it direct from kenlowe tho works out cheaper thier number is +44 (0)1628 823303

Hope this helps
Barney