that is a small case and i am not sure what will fit. you will need to do some spec gathering before we can offer solutions. need to know about the power supply, what make, model is it? this is the most important thing that will limit what card you can use unless you want to replace it.
second is how much room is there for the card? measure from the back of the case where the card will stick out to the first thing it will hit. some small cases will limit you to short cards. second thing to look at is how much room is around the slot. is there room for a double slot card?you'll want about 1.5-2 inches around the card for an average double slot card, otherwise you'll need a single slot card.
check on those specs and measurements and i can offer some options for you.