What exactly would I need to replace on my car to give the exhaust a
deeper, tuner style sound? Is it just the end of the muffler or do I
need a whole new exhaust kit? Thanks!

a larger diameter pipe will add to its tone. and volume AND performance.

the catt and muffler combo will change its tune quite a bit. i would go around and try to find a simular car as to your and see if its mods sound good to you. if it does then copy if the owner will tell you what was done.

in a turbo car i found the best sound to be a 2.5 exhaust followed by a high flow cattalitic converter followed by NO muffler.

the turbo will knock out so much sound it will drop your jaw.

i run a turbo on a 2.7 88 legend with the above system.
it is quiet enough to hold a comfortable conversation in the car and the man has never hasseled me about it.

maybe go to a exhaust shop and see how much it would cost to remove your muffler...also ask how much it would cost to put it back if you dont like it :)and save the old muffler.