What year? The year is important, as the compression ratio is different across year models. The 99 RS that was built up by Shiv in Sport Compact Car magazine easily held 294 HP to the wheels, for tens of thousands of miles, on stock internals. However, the MY00 and MY01's have a higher compression ratio and more brittle pistons and rings (as I recall). As a result, high power in the 00 and 01's will be potentially more devestating.
Of course, detonation is the killer. Any about of knocking/pinging in your ignition system will quickly destroy any engine, no matter how well built. High octane and proper ignition timing can combat detonation, but not necessarily cure it.
None of the stock 5-speeds can handle very much power, at least not second gear, and especially not if you are power shifting. There is quite simply too much torque and the gear disintegrates. However, the 4EAT is purported to handle upwards of 600HP with some work, such as a valve body rebuild, different torque converter, and heavy-duty clutch packs.
That was a Tony Rigoli built motor that ended up as a 2.7L and a serious amount of money in it. Like around $10K on the motor alone but hell if you have that kind of money to spend then go for it but I damn sure won't spend $10K on a motor unless its a twin turbo LS1 crate engine.