Also keep in mind that towing capacity is a very hot topic here (and I am just going to throw jet fuel into the fire). There are really 2 completely divergent schools of thought
1) that towing capacity is a semi arbitrary rule of thumb based on a 50 year old semi arbitrary rule of thumb made by the NTSB (in the days of the 57 Chevy) based on no real scientific data and that modern numbers come from the marketing or legal departments of car companies, not engineers. People of this school of thought tend to agree that there are many factors such as: will your insurance cover you if you are over, horsepower, gear ratio, speed, wind resistance, aerodynamics, wheelbase, tire thickness, hitch design, weight inside the towing vehicle etc. Some people will find a tow vehicle trailer combo that is 500lbs under capacity will drive worse than another completely different pair that is 500 over capacity.
2) that towing capacity is a law or commandment or something like that and that even the smallest trailer needs a big diesel pickup truck to be able to handle it properly and that exceeding it by even a few pounds would be catastrophic.
My advise would be (assuming insurance is not a factor) is to use the towing capacity as a rule of thumb and talk to someone experienced in making custom hitches (not installing hitches) about your specific situation, and potential car/trailer combo.
If you want to understand some of the other factors involved in a Tow Vehicle/Trailer pair, take a look at these articles. This guy is considered by many to be one of the most knowledgable people in the world on towing. He has done extreme pairs such as a Mini Cooper/Airstream pair (but don't judge this one until you have read the article, you may still disagree with this one after reading it, but may be surprised on the thought process involved), but very few people understand better if/how they will pair up
http://www.canamrv.ca/hitch-hints/