As a bit of an example i guess.. I have a Hi-flow cat (a little short one), a nice long resonator in the middle and a straight through oval shaped muffler at the rear. All done in 2.25 inch dia. mild steel and I had a 2.5 inch chrome tip put on the end to make it look nicer.
All up this cost me around $550 at my local exhaust place and they did a fantastic job of installing it.
The car now breathes heaps better upwards of 4000rpm and it sounds fantastic. It has a nice deep note (not tinny at all). It's still reasonably quiet when cruising at up to 80kph, but if I knock it back a couple of gears and sink the boot in, you can hear me coming a mile away. The noise at 100kph is reasonably quiet in 5th gear, but being back in 4th when climbing hills at 100kph is pretty loud. Doesn't bother me too much though, I just turn the stereo up!