A graphics card does not replace a render farm.
no it makes the human more productive.
graphic accelerator => faster worker (that is if he doenst have a good enough gfx card)
cpu => power to brute force.
but yes thats < over simplification, youd have to understand how computer hardware works to really get the answer.
i am thankful i didnt buy 4800
It depends on what you do really, if your serious of 3d then you should think quadro 3800. 4800 or 5800 and accept no substitutes. But offfcourse you must be in the moving picture or tv business and be able to cut those out in taxes. But thenagain if your serious about 3d youd buy 2 4000$ computers in one go.
Pesonally id say if you buy a maya licence and dont buy a quadro your kind of misusing your money.
or is there no solution to expensive stacked render farms which individuals cant afford.
you can hire farms. Thats falls in the same category as the previous questions tough you would have to understand what the computer does when it renders to bring the rendertimes down. In any case i would say that for MOST of us the farm is actually not a cost factor, its actually a investement that pays itself back in your ability to do the work in firstplace.
PS: throwing cash at the problem doesnt help if you dont know what the problem is.