Let me clear a few things up that have been posted in this thread. First up, Impulse69, there is ALWAYS a reason for BSOD's

and generally the error code created by them will tell you what it is.
As far as EIST aka speed step, you are 100% safe leaving it ON. There is NO reason to turn it off unless you are pushing to the ABSOLUTE max *think 5.8ghz + on SB chips with tons of voltages* aka things that aren't done much on these forums <3.
With that being said the best way to stabilize SB chips is through vcore. If you run LinX with AVX pack your temps and stability will REALLY be tested. P95 is a decent app, but it doesn't even come remotely close to stressing a system out like LinX or IBT with AVX.
If you aren't sure what AVX is, it increases the GFLOPS and stress through the system. LinX/IBT are also mathmatically A LOT more stressful then P95 and you WILL see much much higher temps, roughly 10 degrees more then p95 temps.
If you run a stability program like LinX/IBT and you fail it, simply up the voltage until you become stable. Now for 24/7 use I wouldn't run more then 1.4 to 1.425 voltage if you want the chip to last forever. If you are going to upgrade to IB and you don't really care about the chip, by all means push the voltages as much as you want as long as temps are fine.
We really don't know the degradation point / limits of SB yet because they haven't been out long enough. I know plenty of real benchers who have ran tons of volts *think close to 1.7* through SB chips and they are still up and running just fine today. In
SHORT bursts you can run
a lot of voltage through SB chips and they will be completely fine *as long as temps are within reason*.
Anyway I am getting a bit off topic heh. Back to the OP Lorddac, a lot of SB chips need a ton more voltage to go from the sub 4.5 ghz range to over it. For example I know several of my chips / bench chips need around 1.35 for 4.5ghz, but for 4.7+ they need 1.4+ vcore. It really solely depends 100% on the chip.
Tweakboy - Running 1.5volts through a SB chip for 24/7 use is NOT a good idea no matter what kind of cooling you are running. For a quick benchmark sure, but for every day use, even with EIST that is a horrible plan

.
Lorrdac - as long as your temps are within reason up the voltage to 1.4vcore or 1.425 and see what the highest stable overclock you can achieve is. You for sure will be able to hit 4.5ghz with ease at 1.4vcore LOAD *make sure you factor in vdrop, for example if you set 1.4vcore in bios and at load you are getting 1.37, then run 1.43 vcore in bios so at load its 1.4vcore*. You can probably hit anywhere from 4.7 to 4.8ghz with 1.4 to 1.425 vcore load from my experience with SB chips *which is pretty vast

*
Wish you the best of luck overclocking man and hopefully you have a great chip on your hands!