I have a Stillen dp that I put on after replacing the clutch last winter. Like someone said earlier, the Stillen is very nice, stainless steel with flex section, larger diameter than stock tubing, flows nicely into a large collecter, and eliminates the front pre-cat and main cat. It also bolts right up to the stock exhaust, flange that the main cat bolts to. I gutted the rear pre-cat while the engine was still in the car, but it took me several night of CAREFULL surgery with a powerdrill and 18" extension. I used a 1.5" diameter spade type drill bit that helped to knock chunks of the cat out. WEAR SAFETY GLASSES AND A GOOD DUST MASK!
The Stillen is made for 1st and 2nd gen. 3SI's and the rear exhaust flange has two sets of holes drilled in it. If you have a '94 or newer vehicle, save your rear exhaust gasket because the ones that come with the kit are for first gen. models. At first I didn't think the bolt holes were going to line up but they did (it has to be just right).
The nice thing about the Stillen is that it's all one piece. No extra sections needed to eliminate the front cat. It all stainless and the welds are very nice. The flex section will help to eliminate vibration and make the rest of your exhaust system less prone to failure (I'm a metallurgist, trust me). It's also got two bungs welded onto it for EGT or O2 sensors, so when the time comes I won't have to drill/tap any holes in it.
That's my 5 cents. Sorry so long.
Jeremy