Dual push/pull configurations move no more air than single fans. However, side-by-side fans will displace twice the air as a single fan.
The key to efficient fan use is a shroud that forces the air across the entire heatsink surface area. A fan without a shroud circulates air around the fan but not around the amplifier.
PAC makes inexpensive 12-volt fans. You can safely run multiples of these off your radio’s turn on lead via a relay.