it is usually air flow being blocked that causes that kind of temperature range. either the gpu heat sink is clogged with debris, or the gpu fan isn't turning like it should because it is clogged with dust. i keep a 550ti myself on standby for the directx11 if i ever need it, my evga 550ti is the sort that directs the airflow out of the back of the case unlike my old 9800gt that just keeps the hot air flowing back onto itself like a convection oven.so its idles at a toasty 60c.
my GTX 2_5 cards hurl the hot air out of the back, and they idle around 50c .
another variable is your case air flow. if there is a mismatch of pressure, , then the interior cabinet heat can accumulate. i have seen users improvise a top exhaust opening with a fan to pull hot air out from the top, and it usually renders cooler interior temperatures that way. Most newer cases have that provision built in, i think the liquid cooled cpu coolers are configured so that the top case fan opening mounts the cpu cooler radiator also.