how did the case get broken?
anyway, hot air rises. I'd suggest you have the fan at the top back blowing out, not in. it may be sucking air in from the power supply also.
other than that, how is your airflow?
my case is very clean, and my CPU never gets above 30ºC (though my case is quite easy to make clean)
you can also get a new video card cooler. the one I got is a Zalman VF900-Cu LED (the one with the fan that lights up blue)
when I installed it, it dropped my cards temperature (XFX 7900 GT) by 10 degrees.
it also fits 6800's