260 is a bit off
It really is in how you drive /shift it. I have a 301 whp 297wtq 03 Wagon with stock trans at 157k no issues yet.....but I dont slam the gears or launch it from a dead stop, and always try and double clutch from high speed to a stop.
Id say 300-325 is the top of the top end HP the trans will take, but I know guys who have blown a stock trans at stock HP
subaru505 all your question are answered in the Trans Facts and minor searching in the trans threads