it is possible! I use AMD GPU CLOCK TOOL to set clock speeds and then load up modified ccc profile with the desired fanspeed. Before you do this you should modify your profile file by delete the part on top of the list whicj contains the stock speeds ( 750 900 thingy on 4870. works wonders Though i cant get my card past 830/1050 without getting some artifeacts in atitool in about 4/5 minutes. It also doesnt help if i set fanspeed to 70%.
ps are somewhere @ 50-60 @ load on 70%
Would it help to get a HR-03 GT?