I'd probably pick the top rig, because you can always expand by throwing in a second card. You can't do that on the bottom rig.
Can't i buy later on another 6970?
Are you using these solely for mining or as a regular PC too?
I would also go with the first one, heres why:
The 6990 card alone can do the same as the 2 6970s in terms of Mhash/s (give a few tweaks here and there). Also powering one device as apposed to w will be less heat/power consumption. You also have the option of getting another 6990 later on if you want to add into it.
My only issue with both machines are they seem a tad expensive. If they are just miners then you can probably cut down on the motherboards and CPUs - ie not get such fancy ones and save some cash.
I agree! But to tell you the truth...
the only reason why i've writen the 6970 in my rig alternative specification is because i've been looking all around the internet and i cant find an "internet shop" that sell the 6990. Apparently all 6990's are "OUT OF STOCK"...
Do you know where can i find one (or even two)?
Thank you all for replying so quickly.