It all depends on your budget and how particular you are about the sound you are looking for.
For about $100-200 you can get new mufflers welded/clamped in and have a nice rumble. Flowmaster, Magnafow, Dynomax, Pypes are one of many companies out there that design quality mufflers.
Now, if you decide to get longtube headers (replacing your "log style" exhaust manifolds for long piping called headers, usually cost $300-700 depending on brand, quality, material such as stainless steel vs. coated/bare steel) they are usually a pain to get installed, but will give your car a ROAR. Combined with a nice sounding muffler, you will have a great sound.
If you want to go all-out, you could get longtube headers, custom exhaust piping (typically 2.5 inch, unless you're making 500+ horsepower) into an "x-pipe" or "H-pipe" if you desire, which is literally a pipe in an X or H shape, your muffler of choice, then that same 2.5 inch piping out the back with your favorite looking exhaust tips. This route can cost roughly $600-$2000 depending on piping used and labor costs. You will get the exact sound you desire, just the right combination of piping and muffler can give you a mild, deep rumble all the way to obnoxious race-car sounding exhaust and everything in between.
I would consider these the 3 basic levels of exhaust customization. Learn what you can about what brand of mufflers sound like what, you would need to do at least a muffler swap to get a different sound. In general, Flowmaster is loud, old school muscle car sound but doesn't "flow" exhaust gasses as well as other brands, detracting from performance gains.. Magnaflow is very tame, but growls and flows excellently. Generally, most aftermarket mufflers flow better than stock and will provide a mild (1-5 horsepower) bump.
-Mufflers. Generally a very small gain. Maybe 1-5 horsepower.
-Longtube headers. BEST gains for exhaust. 8-15 horsepower.
-Decent piping. Generally 2.5 inch for most performance cars, expect a few horsepower. This allows exhaust to flow better.
-Tips. As long as you don't get tiny 1 inch Chevy-Bow tie style exhaust tips this shouldn't have any real impact. Almost purely cosmetic. Pick what YOU like best!