Dead PSU = time for an upgrade. 850W too much?

[cable_cat]

My PSU died on the weekend and I've decided that a more substantial upgrade to my system is long overdue. I need my PC up and running ASAP for work so I'm hoping to purchase a PSU that will run my current system (while I wait for parts) AND in my upgraded system. The old PSU was 800w so my first thought was the EVGA Supernova 850w G2. However, pcpartpicker has suggested that a wattage as low as 500 would be ok in my upgraded build.

Approximate Purchase Date: PSU ASAP, the rest in the next ~2 weeks.

Budget Range: $1000-$1500 USD

System Usage: Gaming and general multitasking of movies/internet/work.

Location: Australia

Overclocking: Maybe.

SLI or Crossfire: No

Parts to Upgrade: PSU, MOBO, CPU, RAM and GPU

Current Build
MOBO: Asus P6T
CPU: Intel i7 920
RAM:Kingston 6GB 1333MHz DDR3 Triple Channel Kit
GPU: GTX 295
PSU: Gigagbyte Odin 800W Modular PSU (RIP)
Storage: WD VelociRaptor WD6000HLHX 600GB 3.5" SATAIII
Western Digital 1TB Cavier Green WD10EADS
Cooling: Noctua NF-P12 120mm Pressure Optimised Silent Fan
Thermalright Ultra-120 Extreme Heatsink + Fan Holder + 120mm Fan
Monitor: 2 x 1920x1080
Case: Antec P183

New Build - http://pcpartpicker.com/p/t7GqFT
MOBO: Asus Z97-A
CPU: Intel i7 4790k
RAM: Corsair Vengeance 8GB (2x4GB) DDR3-1600
GPU: MSI GTX 980
PSU: EVGA Supernova 850W G2 (???)
Storage: Keep from old build
Cooling: Keep from old build
Monitor: Keep from old build
Case: Possibly keep from old build (lacks front USB 3.0 ports) - Recommendations?

TLDR: What Wattage PSU would be suitable for both my current AND upgraded build? Any Case recommendations or suggestions/advice on my new build would also be appreciated. Thanks.

 

[Macko939]

I am running pretty much the same setup as your "new build" (the same mobo, CPU and GPU + 16gb of the same ram) and I run it off 650W no problem, calculators say that as low as 500W would be enough for it anyway.

 

[vishalaestro]

i would suggest you to refer the psu tier list v2 under the components so that u will come to a conclusion.personally going with seasonic psu's is the best choice