Here's my strategy, Mind you that it's very expensive, but it ALWAYS works. ALWAYS:Take 2 PIC Sydneys (and maybe an engineer to take out C4 and mines that might be placed), and get to the NOD tunnel that is right in front of the PP, but stay in it, and wait.
Then, 2 Mammies or 3 Med Tanks with a few engineers set up a barrier at the top of NOD's ramp.
The NOD will get a bunch of guys, and try to take out the tank assault. While this is going on, the 2 Sydneys shoot like hell at the PP and the engineer can try to sneak in and plant C4 on the MCT for a bit of extra damage, and he can get past the turrets most of the time since they should be occupied with the tanks. (The engineer can always stay with the Sydney's to heal them if they take any damage for some reason).
If the Sydney's are discovered and killed, the tanks should be able to turn the Obelisk into a wreck, and the NOD will be rushing to fix their PP.
Works every time. Either their Obelisk is wrecked, or their PP is blown up and the Obelisk doesn't work.
Either way, their defenses are down, and with the damage GDI has made, they should be able to buy some Mobile Rocket Launchers and Med Tanks, and some powerful infantry, and can take out the base WITHOUT even using a Beacon.
EDIT: For the Sydneys, you can take along an advanced engineer and place prox mines on the Sydneys before you head out, reload, and put prox mines near the NOD PP entrance. This way, the prox mines protect from the enemy coming too close, and the Sydney prox mines can be used if the PP is destroyed before the Sydneys are found, they can run out and do some damage on the barracks, going on a suicide run at the same time.
[ April 26, 2002: Message edited by: Tyrant *Beo* ]