My PC Build is :
Intel i7 6700K
ASUS Z170 PRO GAMING Mobo
32GB RAM (Corsair Vengence 4x8GB)
ASUS NVIDIA 1070 GTX DUAL
Antec VP600P PSU
I am planning to get another 1070 GTX card for SLI, will the existing PSU support is sufficient for 2 way SLI or should i upgrade my PSU also?
According to http://www.pcadvisor.co.uk/feature/pc-components/nvidia-geforce-gtx-1080-vs-gtx-1070-vs-gtx-1060-3640925/, the 1070GTX has a TDP of 150W. This is the amount of heat a component produces -- which with solid-state circuitry is conveniently the amount of wattage it draws, 1-to-1. Doubling that (for two of them), gives you 300W. If we assume that's all on the 12V rail (worst-case scenario), you're asking for 25A from your power supply. Your CPU has a TDP of 91W, and lets go absolute-worst-case scenario and say your motherboard is 89W to make the math easy. This is a further 180W of power draw, or 15A @ 12V. I don't know if it's all from the 12V line, but this is the worst-case scenario.
A single rail (your PSU provides two) produces 30A at 12V, and a maximum of 540W @ 12V combined. Going from my worst case scenario, you are at 300+180W, or 480W of a maximum 540W. Antec quotes a 100,000h MTBF @ full load -- which means you can go bigger still. Your PSU can actually provide enough power for your CPU @ 100% load, several HDDs & fans, and a pair of stock-clocked 1080GTXs.
