Yes we understand. But in order for us to recommend the best gpu, we need to know the other system specs, INCLUDING the psu and cpu.
If your psu is low quality and you put in a high end gpu, the psu will explode and fry your computer. None of us here want that to happen to you, so we need to know whether or not you have a high quality psu that can handle a high end gpu.
Same goes for the cpu. If your cpu is "a crappy one," then when you put in a high end gpu it will get bottlenecked by the processor and the gpu won't be running at it's full potential.