The stock head gasket on my 02 started leaking running at 510 hp, and 48psi on a single turbo. This was with studs. Granted it was after about 300 1/4 passes. I have about 1200 1/4 passes since o-ringing the head without a problem. The last 1000 or so have been at ~640hp. People have gotten away with more hp, but I didn't, and of course people have gotten away with less.
Third gens are a completely different animal. My 05 (see sig), has the stock MLS head gasket. 600 hp on the stock head bolts and gasket are not uncommon, and 800hp with the ARP 2000 studs seems to work. Above 800hp and the New Age 625's are a good recommendation.
The ARP New Age 625 studs are a significant improvement over the ARP 2000 studs, but it does come at a price. I do not know how much they would hold with the stock head gasket on a second gen. The recommended torque on the ARP 2000's is 122 ft lbs. ARP recommends 150 ft lbs with the New Age studs. The New Age studs feel much more solid when torqueing them.
If you are going to do a MLS gasket on a 2nd gen, block and head prep are a must. If you are going to go to that much trouble, just o-ring the head and use a stock gasket with studs.