As a cat lover myself, I appreciate your desire to have a cat (or two). Unfortunately, your allergies are there with you to stay; they cant be easily gotten rid of. But, there are ways to help mitigate the situation so you can live with your cat in relative comfort.
There are medications you can take to relieve allergy symptoms. Some are OTC ( over the counter) and some are prescription. Allegra, claritin, benadryl, all are examples of medications to relieve allergy symptoms. There are others, and in consultation with your doctor, you can find the medicine that works for you.
Its the dander of the cat (fur, residue from skin) which makes you have that allergic reaction. Once you have the cat, there are environmental measures you can take. They include not allowing the cat in your bedroom, getting an HEPA air filter, frequent vacuuming. Having the minimum amount of textiles also can help as they accumulate dander. That means avoid heavy upholsteries, rugs and carpets; stick to easily washed wood floors. Wash the blankets or other bedding your cat frequently lies on.
There are allergy shots also, to try to desensitize you, but they take quite a while to have an effect, and success is not always guaranteed.
You may want to experiment with this prior to actually getting the cat, realizing there is no way you and the cat can live together and then have to go through the emotional trauma of having to get rid of your pet. Try calling various animal shelters and organizations and see if you can foster a cat; this way if it doesn't work out, the cat can readily be taken back by the agency.
Here is some more information: http://www.thecatsite.com/Health/223/Living-with-Cat-Allergy.html and this is a site which discusses fostering cats: http://purebredcatbreedrescue.org/fostering.htm
I hope I was able to help,
Susan (and her two cats)