There is something that is being left out here... gas mileage. In the suby turbo motor, cruising in 5th on the freeway (under the turbo) with a 300hp STI 2.5 yields you around 25mpg in even the heavy STI (and that was in my buddys tuned STI making 415hp). Imagine what you would get with a teener.
Power... The setup that I am going to have built (when $ ever gets here) will rev upto 8k, make 450hp on pump gas, and even more torque. Not to mention that peak torque is made around 3000 rpm and continues like a New Mexico butte until about 7000. All this for about the same price as a 993 varioram. All the internals are balanced and forged for strength for years.
Tranny... WRX 5speed with a gearset from PPG. Total for the tranny will be around $5k but it will handle upwards of 600ft/lbs of torque and will shift "dog" style which is way the crap faster than any of us could shift. It would be even cheaper with synchros.
All in all if you are looking for power, a flat torque curve, the great sound of a high power "boxter" style engine, smooth shifting, low weight, great gas mileage, and all around kick-assness, you can't turn your head away from Subaru power.
If you want the sexy "porsche" sound then and you want to preserve the porsche nostalgia, by all means, go with a -6.
Thats just my $.02