Need new cooler and lower that voltage!
Find an Antec 920 for cheap somewhere or pick up a Corsair H80. If it's really only a few degrees off a H100 then I think you will find it quite pleasing. I know I love my H100. Shaved 4-6c off my NH-D14.
Don't use a game for testing overclocks. Use Intel Burn Test. Much more stress on the CPU and RAM.
For example. My setup shows high temp of 71c in IBT on Max burn but in games shows only 55c. Now you said you saw 90c+ playing GTA4 so add at least 10c for the IBT runs.
Look into using IBT to test your overclock. You won't need to guess if it's stable anymore, it will just crash instead.
but ya, i'll look into the h80. hopefully it's better than the d14 or silver arrow.