i'll elaborate on the catco i got, it's the 5inch stainless one with flanges for a 3 inch system... it flows so much that last time my car was on a dyno there were flames
for some reason (mainly price) people don't like hks, trust tomei dump pipes... i have the following exhaust setup and while it was not cheap, it has been rock solid...
hks split dump -> blitz front -> catco stainless cat -> fujitsubo power getter
all stainless not too loud, flows well, no creep and does not hang low to the ground...