GTX680 Over Clocking Issues

I have 2 EVGA GTX680 SuperClocked GPU's in SLI (Base:1058Mhz Boost:1124) both on water.

I haven't been able to get decent, stable over clock on either card using the Precision X software provided by EVGA. The most I have gotten is +100mhz on the GPU clock offset and even that wasn't 100% stable.

It didn't bother me in the past as much since the 2 cards were already overkill for my 25in monitor but I recently purchased a 27in Dell U2711 2560 x 1440 monitor.

In some instances the FPS occasionally drops below 60 in Battlefield 3 (everything ultra) with this new monitor.

I really want to over clock the memory on the cards to help with the higher resolution and also because I have so much thermal head room for the water cooling system that is going to waste. The cards only have a 15°C delta temp with no OC.

I have gotten the power target to 132% the GPU offset to 100Mhz and the memory to 300Mhz and passed the Precision X benchmark once and saw a massive performance increase. However, as soon as I try to run 3DMark11 or play a game the video drivers crash.

I have tried reinstalling the latest drivers but it makes no difference. BTW anyone notice Nvidia updating their drivers a lot less frequently?

I have watched a bunch of videos online where people are able to get +200Mhz GPU offset and +500Mhz on the memory no problem.

If anyone has had this issue with these cards I would be very interested to hear about it.

Would using an alternative over clocking software like MSI afterburner make any difference?

Thanks in advance...