its all in the tuning.
some folks make 300 whp on stock motors reliably for years
some folks blow up on 200 whp built motors in a month.
90% of bottom ends that blow up do so because of detonation. detonation is 100% caused by improper tuning, either fuel or ignition (or, say bad/wrong octane gas).
5% are mostly from boost spikes, which in turn, make the motor run too lean, and thus, detonate.
and the other 5% comes from shit just letting go. be it oil pumps, a weak rod, etc. all things break.
half-assing the fuel setup is the worst thing you can do.
PSI is irrelevant to power for the most part. each turbo is so very different. saying 6 psi is meaningless.
6 psi out of a t25 is like 30 horsepower (figure of speach)
6 psi out of a t999 is like 3000 horsepower (figure of speach)
turbos compress air. the larger the turbo, generally, the more dense a given volume of space is. more density = more air in 1 given uint of space. how MUCH (volume (cfm) ) air gets in is what makes the power. The RESISTANCE (pressure (psi) ) as measured at the map sensor, is technically, the air NOT getting in, or what's fighting it to get in.
you suggest a T3. that's fine, but there's at least 1000 T3's on the market. some are small, some are pretty large, and some even have a 60-1 wheel in the compressor.
If you're going for a smaller t3, like a t03 .42/.48, i think you will be more than fine with the stock 240s, the missing link (or other map bypass check valve) and the 12:1 fmu.
If you're going for a larger T3, like a t03 .63/.63, i would then suggest running the 280's, the missing link, and the 12:1 fmu
if you're going for a t03/60-1, i suggest making the jump to a hondata system, or uberdata, etc along with some 440 cc injectors and some dyno time to tune it in with a tuner.
As for clutch, I'd at least go to the stage 2, and the stage 3 if you are going for the larger turbo.