i have tried oc my mx400 (dont know the brand and has a fan) before too...i used the rivatuner software
my default core clock 200 and memory clock 286, i oc the core clock to 240 and memory clock to 340....i played online game for a while and it worked fine. however, the performance wasn't increased that much. i run 3d mark 2001 SE and it scored about 300 points more...
but sorry...i havent looked at temperature really so cannot tell you