Okay, you have 3"thrush mufflers and dumps before the axle. And now you want tailpipes and more aggresive sound? Of course you realize that tailpipes will tone down the sound you have now.
First, what thrush do you have now? Thrush makes all three muffler types. There are three, straight thru, with a sound absorbing packing, (which can blow out, making them louder over time) triple bypass like turbos and hemi mufflers, and chambered style, flowmasters spintech hooker aero etc. You need to listen to other cars to decide which sound you like, they are all different, and start shopping for that style. The easiest to tune for sound volume would be the flowmaster type. In a fixed size, more chambers-less noise, fewer chambers-louder. I personally like the flowmaster sound, many dont, and the louder ones do resonate annoyingly.
Next, its a generalization, but shorter/smaller equals louder. Turbos generally have a minimum size, but straight thru and "race" chambered style can be almost as loud as wide open pipes. If you go with a set of mufflers that ends up being too loud, you can also run resonators in the tailpipes to tone them down.
Just as a personal aside, i currently have a (somewhat) fast car, with two of the three muffler types. I love the sound of my flowmasters with full tailpipes (even tho they are huge, no resonance). I used hooker aeros on the fastest car, didnt care for the sound much initially, but i got used to it, and i really like it now. The third car has staight thru magnaflows that are amazingly quiet, but they are huge long mufflers, straight thru can be amazingly loud if thats what you want.
So, pick the sound you like, do some shopping for the sound volume you want.