Not too sure about that PSU actually, it seems to only have one 6 pin PCI-E connector - which isn't enough for your card.
I believe the 6870 is connected with 2 x 6 pin connectors, while the Power Supply you referred to comes with 1 6+2 pin. Could you just verify that for us? I remember VTX having two versions of the card, 1GB and 2GB, do you have the full description of the card?
I'd go for the second one in my post, it has four 6+2 connectors (You can plug a 6+2 cable into a 6-pin port). If your video card does have 2 power ports then it *should* be OK.