GTX 680 Overclock

[Dawgdoc]

New rig less than 1 week old as follows:

CPU: I5 3570K
CPU Cooling: Thermaltake Extreme 2.0
Mobo: Asus P8Z77- Deluxe
Ram: 4 x 4 GB G.Skill Ripjaws DDR3 - 2133
GPU: EVGA 680GTX FTW 4gb
http://www.newegg.com/Product/Produc...82E16814130798
PSU: Corsair HX850
Storage: OCZ Vertex 4 SSD 512gb
Case: Coolermaster HAF XM

CPU is overclocked at approx 4.55 Ghz. Would actually like to go higher but I either have alot more "tinkering" to do with UEFI bios and s1155, or I just have an average overclocker. A story for another time.....

Ive just started messing around with the GPU.

Currently using MSI afterburner for the overclock, and stability testing with a variety of different programs including:

MSI Kombuster
Heaven
EVGA OC Scanner
I think there are 1 or 2 more but Im at work and cant remember.

On to the questions!

What approximate ranges for overclock should I expect from this GPU?

I seem to be able to achieve what appears to be stability in ALL GPU benches/stability tests, but when I play games It quite obviously is NOT 100% stable.

I think Im getting stability at approximately 1350 to 1375 on the Core, and up to 1750 on the memory!! ?? !! This seems UNUSUALLY high to me. But again, when I play video games some of the games I play will hang and obviously not be stable.

Suggestions for:

1. Typical range of OC for this card.

2. Any other stability / bench programs

3. Aftermarket air coolers for this GPU

4. Expected safe ranges for voltage increases after the aftermarket cooler is applied.

All of this info greatly appreciated