My prior XI was right around 620 awhp/620 wheel torque. Day to day driving, it was fine.
From a track/drag strip standpoint, the front diff, and shaft in my case proved to be the weak link. I blew up the front diff on 2 separate occasions launching at the track. Torque level the first time as about 620 or so, the front diff exploded, and the front driveshaft twisted, causing a horrible shake at cruising speed.
The second attempt at the track, the car was dialed down to about 575-ish torque and it still busted.
That being said, the car ran and launched perfectly at the track around the 500-520 wheel torque level for an entire season.