[Quickurt]

I downshift only to be in the correct gear to accelerate into, through and out of a turn.
In the supposed "good old days" we would downshift to save the brakes from excessive heat and/or wear, but those days are long gone.
LB hit that nail on the head.
With Boxster brakes, you're actually wasting precious braking concentration on screwing with downshifts and probably screwing up your stopping/slowing distance.
If braking properly, you don't have time to row through more than one gear anyway. Stand on that center pedal, double clutch/heel toe down into 5th gear (4th in a base model) and you're already down to third gear speed. Before you can get it into another gear, you're nearly stopped.
You're better off spending that precious brain matter calculation time estimating the gear you will need to be in for the corner you're approaching and then making that one shift - smoooooooooooooooooooooooooooooooothly - and being in that gear BEFORE you' re done braking.
I have a set braking point for the turn in to my subdivision entrance road. From 70 mph I brake at the beginning of the previous driveway - 75 ft from the beginning of our entrance road curve in. I stand on the brakes, downshift from 5th to 2nd while gently turning in (loving the Porsche anti-lock system) and end up in the driveway, on the proper side of the road, at our 20 mph subdivision speed limit. The entire process takes maybe 3 seconds.