Now replacing original OEM for Like quality or just slightly better build than OEM components is a smart and cost effective way to go. That being said... my XJ has been living in it's new hotter and humid climate for just over the last year now. In a massive city.
On days where it's 105 on the dial and 90% or above humidity... sitting in traffic she'll creep up just over the 210 mark but not to the point where the aux fan kicks in... and goes right back down once moving again.
I do have basically everything cooling replaced except the fan clutch which is still in very good nic doing it's job the right way.

I wanted to comment on your post because of the last statement you made Mark.... amen to that. The answer is not what can I upgrade so that hopefully it will make it better... first you have to identify the problem or you're just loading the parts cannon and that gets expensive in a hurry most times. And often doesn't end up fixing a darn thing.

 

Bingo.

Intelligently done upgrades can be great, but that's not the way to fix a basic problem.