From what I have seen on the M17x R3, to run on 4.5Ghz or higher, one needs to increase the Flex (voltage). By run, I mean literally run at 4.5Ghz all cores, so that Throttlestop would report a constant 45 FID. The BSODs you are getting indicate that the CPU needs more voltage.
From my experience @ 4.5Ghz I needed 6 Flex, 4.6Ghz I needed 12 Flex. The Vantage score on 4.6Ghz was the same as 4.5Ghz 'cause temps on 4th core was 100C, chip was just not coping. 4.5ghz seemed the max possible I could push it as the cooling in the M17x R3 is just not as good as the M18x - mw86 - you should borrow someones M17x R3 and give yourself a challenge, it's very different to the M18x.
1000 PriPlane, 6 Flex, 10019 BCLK... 4.5Ghz - http://i191.photobucket.com/albums/z92/chaotic_george/VantageTemps.png
1000 PriPlane, 12 Flex, 10019 BCLK... 4.6Ghz - http://img190.imageshack.us/img190/4352/98361236.png
@OP. I can guarantee you that with stock cooling you will not be able to run the 2 Vantage CPU tests at 4.6Ghz. You will get a thermal shutdown.
Also OEM vs QS comparison, when set at the exact same settings I noticed the OEM chip getting a better score (but then again that was probably a better chip in general). It would be fun to do a more in depth comparison though.