The price of 3870 X2 will be between 399 and 499 USD/EUR, 249 and 299 quids (yes, life sucks in Bligthy).
RV670 chips are working at 750+ MHz each. 775 MHz should be reachable by launch time. Who knows, maybe even 800 MHz for the GPU. When it comes to overclocking, we have no idea at the moment, but the memory should be able to work at 2.25 GHz, yielding in combined bandwidth of 144 GB/s. Not too shabby.
This card will feature 2x 512MB GDDR4 memory, 2x DVI-HDMI and DisplayPort. NVIDIA's next high-end part will also be a dual-GPU card.