Compare Dual 8.4 vacs VS Quad 2 stage.
The two machines are close in vacuum
Two 8.4 vac
VS Quad 2 stage Max vacs
You will learn amp draw is king and always tells you the winner in performance
Two 8.4 draw about 26.8 amps and quad Max vac draw 30 amps.
Dual parallel 8.4 = almost 41,487 vacuum units and quad max 2 stage in a series parallel configuration = 42,500 vacuum units. Vacuum units are calculated by Max CFM @ zero inches of lift X (times) max inches of lift at sea level at zero cfm.
The Goliath is a winner by a hair. The Goliath is a pressure feed system so the water starts off 10 degrees hotter than suction feed extractor unit.
The water temp is boosted 30 degrees by the heat exchanger, hits the pump and electric heater for another 20 degree rise. In side by side comparison if I take a suction feed machine and hook it to the sink at 110 degrees F it will clean at about 100 degrees F. The same 100 degrees on the Complete Heat cleans at a consistent 160 degree F. Using the formula that water molecule vibration exponentially doubles every 18 degrees means the Goliath has 8 X more water cleaning power than a non heated suction feed portable.
Comparing the 12.5 amp booster with dual 8.4 would be a 40 amp vacuum system and equal the vacuum on the Mytee Escape 40 amp vacuum system.
You can add the booster system to the Goliath Flood pumper model but where do you stop adding more power requirements...
The Goliath will run 200 ft of 2" vacuum hose.
The Goliath will not heat cold water rather is designed to boost already hot water. If you want propane, this is good but many customers like to cut the propane bill in half by still using the customers hot water to start, use the Goliath to boost the temp and then the final heat by propane. I cost way less to heat 160 degree water than 60 degree water.
The Goliath offers water extraction option with a much larger auto dump system that most other portables.
Any machine can be used with the Little Giant heater. You have to leave the heater outside during use. Taking 60 degree cold water and converting it to 200 degree hot water is huge and offers over 2000 times more water molecule vibration and cleaning power.

Complete Heat Portable
Mytee Escape
Dual 8.4" vacuum portable.
Cross American Jaguar 8 4 Auto Fill Auto Dump 800 Psi Carpet Cleaning Starter Package - Jaguar 8 4 -
Starter little giant heater