When I used to have mine at 4.5Ghz it took a 1.300 Vcore voltage. Some people may need a little less. But YES, you will have to raise your voltage to get to 4.5Ghz unless you have the best chip Intel every built. And if you go higher than that you'll need even more. For instance, I have mine at 4.7Ghz@1.380Vcore and that's a lot more than the 1.300 it takes for 4.5Ghz.
And just cause you run prime95 does not mean your stable so be careful about that. I can run my CPU at 4.7Ghz with only 1.280 Vcore and get through prime95 for a little while but as soon as I run prime95 AND a game, it crashes. So to test overclocks I recommend running Intel Burn In Test for starters along with COre TEmp for temps and while your doing that, play a game. That's the only way I know for sure I am stable. Also check if you have any WHEA errors in event viewer. Because I dought you are fully stable at 4.3Ghz with no voltage increases whatsoever.