Plan is to go true dual. With 2 1/2in in/out with DYNOMAX Race Bullet Mufflers (24246 or 24215) and 2 1/2in in/out WALKER SUPER Catalytic Converter (15033) with a 3in Tip at 45 degree angel. (yes i do want to upgraded my headers but for now just the exhuast system. Now I need some advice(well more so inputs on what you guys think)

to small of a pipe?
should i stick with stock cat?
stainless steel or just steel?