the car sounds like a tractor will strait pipes. You will need atleast a muffler to keep a quality sound. The strait throughs are not a restriction and will keep a nice deep note. Magnaflow and borla are the best matches
Poke around on youtube. There are many combinations out there. I like the 2.75 catback systems from Blueflame and Jetex best. Unless you're going big turbo, anything over 2.75 is less beneficial and "bother the neighbors/attract police" loud anyway.