The more efficient the cooler then the lower the intake temps and denser the charge. If you are running anything more than standard power then I think going bigger or more efficient than a 4x4 is important, especially when your climate will be hotter when its summer.

The RS500 had a much bigger cooler for a reason, Ford would not have put all that expense in just to make it look good.

I would look at the Airtec site and see what they offer and maybe monitor the intake temps. I believe you want to aim to keep under 50 degree C and the lower the better.

It was minus 2.5 degrees here yesterday and my intake temp was hovering around 10 C, when I pushed on in low boost (around 400bhp) it was going up to 20 and sometimes 30C, then in high boost I peaked at 45C. This is on a massive 100mm thick Airtec which has a scoop at the bottom and the whole front of my car is sealed to force air through the cooler and then the bonnet is lifted at the rear to let the air out.

I hope this helps.