How much power [consumption] does a custom water cooled loop add?

I'm pretty set on getting a SuperFlower PSU. The Leadex II 650W is $80usd, or 750W is $100.

1. If I have a i7-6700k and gtx 980ti or 1080, both overclocked. Would I be able to get by safely with 650W or do I need more?

2. How much extra power is needed when adding a pump? I assume I just need to determine how much the fans and pump contribute to power. Can someone provide clarity? thx.