If you want a better overclocking experience get the R3E.
Personally i would go with the R3E i made the upgrade from the Rampage 2 Extreme, I and love my new R3E.
the R2G is a great board buy you are limited on your SLI/CrossFire capacity.
The Rampage III Extreme has many more features than the Rampage 2
here are some to list:
MemOK! (Built in Memory tester)
Onboard Switches: Power / Clr CMOS ( u have this already)
USB BIOS Flashback ( update bios when board is off or not postable via USB flash drive, very handy!!!)
ROG Connect (remote Overclocking through a Laptop/Tablet/Phone via USB or bluetooth connection)
RC Bluetooth (see one up ^)
ProbeIt (temp/ volt monitoring, u have this)
ROG Extreme Engine Digi+ (Very good for CPU overclocking, more stable power to the CPU
iROG (u have this, its a built in chip for overclocking software)
CPU LeveUp (u have this, not very useful if u manually OC
Extreme Tweaker (currently on the RIIG)
Loadline Calibration (currently on the RIIG)
Voltiminder LED (currently on the RIIG)
COP EX (currently on the RIIG)
ASUS C.P.R. (currently on the RIIG)
ROG Extreme OC Kit (Power leads to read voltages with a multimeter or external device)
ASUS Fan Xpert (currently on the RIIG)
ASUS MyLogo3 (currently on the RIIG)
ASUS EZ Flash 2 (currently on the RIIG)
ASUS CrashFree BIOS 3 (less bios clearing needed with this)
Q-Fan Plus (currently on the RIIG)
ROG BIOS Wallpaper (cool wallpaper included on driver CD)
ASUS Q-Connector (currently on the RIIG)
ASUS Q-LED (currently on the RIIG)
ASUS Q-Slot
ASUS Q-DIMM (easier memory installation and removal)
4 PCIe 2.0 X16 with CrossFireX and 3-Way SLI Technology support ( with the ASUS ROG Expander the R3E supports 4-Way SLI