Matt, I've had discs all around on my car since 92. The front is stock Ghia solid discs, the rear is stock 914 solid discs. This provides more braking than you could ever need in any VW.
Only once did these brakes not provide the braking I needed. At the time I had probably 1000 lbs of cargo in the car. All I will say is that there was no damage done at that time.
On top of your stock T3 discs, just add the solid rear disc kit Airspeed sells. This is virtually identical to what I have and will save you big $$$$. Not the sexy red calipers or slotted rotors, but all you need.
Consider that with our cars the rear weight bias is about 60-65%. Everyone has heard the saying that the front brakes do most of the braking. Not as much with our cars. We can afford to have much bigger rear brakes than any front engine car, and really use those rear brakes. The result is that properly setup, a Bug with 4 wheel discs can stop better than almost all new cars made today.
Go over to the German Look web site and spend some time in the brake section. They won't even let you in the door unless you have stock 944 vented discs all around. Then they advocate bigger 944 Turbo brakes. They don't stop there, some idiots go for 928S4/944 Turbo S brakes. All it is, is a competition where they are saying, \"my penis is bigger than yours\".
Don't get caught up with that stupidity where all they are doing is adding massive amounts of rotating weight to their cars.