Alright guys, so here's the deal:
I know next to nothing about graphics cards and power supplies, but I've done a little bit of research.
I looked at my power supply and wrote down all the info on it which are as follows:
Output +12v 15A max +5V5B
Max power +5v 20A max -12v
300W +3.3v 18A max
+5V 3.3V output cannot exceed 160W
I have the serial number too, if need be just ask. But for now, if anybody could recommend some cards that are compatible with my computer, I would be greatly appreciative!