whats the best UPS for MY system

For a system using a single ASUS GTX 770 graphics card a minimum of a 600 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 33 Amps or greater and that has at least one 6-pin and one 8-pin PCI Express supplementary power connectors is recommended.

For a system using two ASUS GTX 770 graphics cards in 2-way SLI mode a minimum of a 850 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 50 Amps or greater and that has at least two 6-pin and two 8-pin PCI Express supplementary power connectors is recommended.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

Overclocking of the CPU and/or GPU(s) may require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

The Corsair TX Series TX850 (SKU# CMPSU-850TXV2UK) power supply unit, with its maximum combined +12 Volt continuous current rating of 70 Amps and with four (6+2)-pin PCI Express supplementary power connectors, is way more than sufficient to power your system configuration with a single ASUS GTX 770 graphics card. It is also way more than sufficient to power your system configuration with two ASUS GTX 770 graphics cards in 2-way SLI mode.

The following are more than sufficient to handle two ASUS GTX 770 graphics cards in 2-way SLI mode:

Corsair CMPSU-750TXV2UK 750 Watts
• OEM: Seasonic
• maximum combined +12 Volt continuous current rating of 62 Amps
• four (6+2)-pin PCI Express supplementary power connectors
• 80 PLUS BRONZE Efficiency Certification
• 5 Year Limited Warranty
• Link: http://www.flipkart.com/corsair-cmpsu-750txv2uk-750-watts-psu/p/itmd5xz5pkgddqmw?pid=PSUD5XZ4YUHYSNNC&ref=2bed710a-0cd2-494b-b425-43a25fbd2f20

Seasonic M12II-750 750 Watts Semi-Modular output cables
• maximum combined +12 Volt continuous current rating of 62 Amps
• four (6+2)-pin PCI Express supplementary power connectors
• 80 PLUS BRONZE Efficiency Certification
• 5 Year Limited Warranty
• Link: http://www.flipkart.com/seasonic-m12ii-750-750-watts-psu/p/itmdhx2hfgf9qhkz?pid=PSUDHX2H645GGHBM&ref=2bed710a-0cd2-494b-b425-43a25fbd2f20


Using a single ASUS GTX 770 graphics card your total power consumption can reach 445 Watts, including the typical 19 Watt power consumption for the monitor, when you're gaming. This estimate is calculated based on the use of a Corsair 850TX PSU that has a conversion efficiency of around 88% at that power draw level.

Plugging the values into the APC UPS Selector returns:

Best Price: http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1500-IN
Best Value: http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1500G-IN
Best Performance: http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1500G-IN

These UPS' output a stepped approximation to a sine wave when operating on backup power. There are some power supply units that will not operate properly with a simulated sine wave UPS. During a power interruption event the UPS will fail to switch over to battery backup mode or the UPS will make some odd noises and report an overload event that will shut down the UPS.

You can also get pure sine wave UPS' that are usually more expensive but don't have incompatibility problems with any PSU.

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SRC1000ICCIND
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SRC1000XLI-CC
http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SUA1500I