Type ATX12V v2.3 / EPS12V v2.91
Maximum Power 780W
Fans 1 x 140mm Ultra Quiet Thermal-Controlled Ball Bearing Fan
Main Connector 20+4Pin
+12V Rails 3
PCI-Express Connector 1 x 6-Pin, 1 x 6+2-Pin
SATA Power Connector 4
SLI NVIDIA HYBRID-SLI Certified
Efficiency Up to 87%
Over Voltage Protection Yes
Overload Protection Yes
Input Voltage 100 - 240 V
Input Frequency Range 50/60 Hz
Input Current 10A
Output +3.3V@24A, +5V@17A, +12V1@24A, +12V2@24A, +12V3@24A, -12V@0.5A, +5VSB@3.0A
Approvals UL, FCC, CE, ROHS
Dimensions 6.5" x 5.9" x 3.4"
Connectors 1 x Main connector (20+4Pin)
1 x 4Pin ATX 12V
6 x peripheral
4 x SATA
1 x Floppy
2 x PCI-E
You didn't mention what else that XPOWER780 PSU will be powering besides the ASUS ROG Matrix 5870.
And that's important because the XPOWER780 is actually a 600W PSU. I know that 780 is misleading but when you look at the data plate this is what you see:
Total output 600W, MAX. output 780W
While the PSU can PEAK at 780W it's continuous rating is actually 600W.
This HardOCP review of the ASUS ROG Matrix 5870 shows the power requirements in a system with an OC'd i7 920 (see page 2 of review for full system specs) range from 437W at full load to 524W with the ROG Matrix 5870 further overclocked.
My opinion is that the Hec XPOWER780 PSU is not a good choice for a serious gaming system and doesnt match the quality or total power requirements of the ASUS ROG Matrix 5870 in a high end gaming system.