300 to 350 is a tough spot for turbos on the SR. TO get there you either need to completely max out your only cheap altermative (s-15 / gtir) to get to 300. and regardless of ball bearign or not you will wear it out faster pushing it to te edge. Or you can buy a smaller GT series ball bearing turbo to get you in the neighborhood of 300, but be maxxed out around 350. but these cost $1500 and up. Or you can go with a T3/T04E setup. depending on sizing and whatnot you can make power at pretty low RPM's (300-3500) they will be more durable than a T25 based turbo, even without ball bearings due to lower shaft speed. this option can net you 300 to 600 depending on sizing and other parts. cost wise expect tobe up near the cost ot the GT series when you are all done.

So there really is no best option, you have to decide what you want, and what you REALLY want to do.

Scott