woah, 1.5? Thats a bit steep to start with dont you think? I'm pretty sure it starts somewhere more around 1.3 MAYBE 1.4. It does suck that the board drops you voltage down, but if you look he is only running at 1.3 with CPU-z. At most I have been getting about a .05 voltage drop from from VDroop kicking in. I mean others have stated different experiences, so it could be anything, but I would definately suggest to play it easy with your voltage, raising it by only .025 at each step, and starting with what you see currently showing up in CPU-z (yes with it lowering it on you, it will take a bit of playing to sort it out, but better to play on the safe side IMO). Just watch your temps that are being reported by Core Temp, and make sure to keep it below 55 at all cost.
Basically you raise your procs up a step or two, check for stability, then go further. When you start getting bluescreens raise your voltage up a bit and check for stability. Its a back and forth process until you hit either your target or you max out your temps. Every time you check for stability, make sure you are constantly monitoring your temps. You can use anything really to kick your proc into full speed, personally I have been using Prime95. Anything to get your CPU utilization at 100%, a few minutes of this should show you how high your temps will go and will help your with making sure it is stable.
Voltage is the easiest way to hurt your CPU, so definately get that better cooler installed before you touch anything serious. Also, it would be good to know what your case is for airflow, because most people can get a minor OC even on stock cooler... so given that you are having heating issues on stock, something seems off. Have you ever pulled the heat sink off after you first installed it? If so, did you make sure to reapply thermal paste properly? Cause it seems to me like you either dont have any good airflow in your case, or something is off with your heatsink on your processor not giving a good contact.
I am assuming that it is doing a forced shutdown and not a bluescreen right? Because bluescreen is usually more of an issue with an unstable system vice something else... just making sure we are on the same page here with what is going on with your system.
As for your intentions to run it as primarily a gaming rig, 99% of the games out there are more bottlenecked at the GPU vice the CPU. If you want to play a game at the best settings, this is where you should try to focus your improvements first. The new Crysis game is one of the few that is actually designed to better make use of multiple cores and such, however, this only starts to become your bottleneck when you get into REALLY high end graphics, like SLI or Crossfire and running more than one GPU. So I still go back to, your GPU should be your primary focus here. CPU's are only used heavily in things like Video encoding, compressing files, and if you are into Folding or some such. The difference between stock clocks and going to say, 4.0GHz is only going to give you maybe 2 to 3 FPS gains.