hey capftp, i wouldnt use overdrive at all!
some people said that after enabling overdrive they couldnt overclock the card in rivatuner or atitool anymore iirc. And in the ati control panel the clockspeed is limited anyways, you cant clock as high as with rivatuner and atitool.

i get around 50-60 under load but thats oced and with a nice and cosy 24 degrees roomtemp