No, Paul, there is no advantage in cooling. The original subs have two 2 ohm coils each to get more power into them. The original amplifier has a "balance" output and runs directly from battery with no step-up power supply, so it is about 35 Watts into 2 ohms for each channel. Thus each sub gets about 70 Watts.

"NeverEnough"'s says run "each door off one channel and each sub off one channel in 2 ohms". That doesn't add up. The two coils in parallel would be 1 ohm and in series 4 ohms. Better to put an amplifier on each coil as in the original set up. Take care, the original subs may fail with more than the original power.

"ppro" doesn't say where to get the signal for the Basslink. One way is to connect it to the signal to the original subs. This signal has the filtering assigned to the original subs. An alternative is to connect it to the output of the radio. This signal is not filtered.