We've seen more announcements on 4GB boards in the past week, ASUS now follows as well with their GeForce GTX670-DC2-4GD5. The cards is based upon their DirectCU II 2-slot design and now thus comes with 4 GB of GDDR5 memory. The memory bus obviously remains 256-bit with the memory itself clocked at a 6 GHz effective datarate (192 GB/s).
The card makes use of a custom-design PCB, with 6+2 phase Digi+ VRM that uses SuperAlloy choke. The Digi+ VRM controller provides a certain degree of software voltage control using the GPU Tweak tool. But as you have been able to read, that will be limited. The core clock is set at 915 MHz, with a 980 MHz GPU Boost.
Monitor wise you can connect towards two DVI, and one each of HDMI and DisplayPort. The 4 GB GeForce GTX 670 DirectCU II from ASUS is to be priced around US $450.