a 1000watts of questionable quality is never enough, the 5870 aint far behind 2x4890 but the 5870 is cheaper and newer then the 4xxx cards and should give you a good deal longer life span then 4890's
here are the specs on it
Type ATX12V / EPS12V Fans 1 x 140mm fan PFC Passive Crossfire Ready SLI Certified Modular No Efficiency 80 PLUS Certified Dimension (L x W x H) 7.0" x 5.9" x 3.4" Connectors 1 x Main connector 1 x 12V (4pin) 1 x 12V (8pin) 8 x peripheral 8 x SATA 1 x Floppy 4 x PCI-E
yeah average quality power supply, a good quality power supply will have active pfc
Are you building from Cyperpower PC? Based on your post, it looks like it to me. What is your budget and I would recommend you build your own, if you are having it built.
if you are correct this will cost $1300~ from cyberpower