4x 7970 vs 2x 770 pros/cons

[dak0003]

I am looking to build a 4k gaming rig. I plan on either:
A. Getting two gtx 770 for ~$300 each and getting a third later on
B. Getting two 7990's for ~$300 each, better performance, no upgrade ability
C. getting 4 7970's for ~ $140 each, basically same as B but multiple cards

So my question is, Will 4 7970's / 2 7990's be enough for 4k, or will I need 3 770's (more $) or I suppose I could even go as far as getting 2x 780's, but will 2x 780's actually be better than 3 770s or 4 7970s? thanks!!

also is 1000W psu enough? 4770k, 2 ram, one ssd, and up to 4 7970's?

 

[Anheanz]

well theres probably not too many games that will work smoothly with 3x or 4x GPU's so if you can i would say 2 780's would be better than 3 770s

 

[Calvin3200]

Major con of multiple GPU's... microstuttering.

I "upgraded" to 3 way SLI not too long ago. My FPS went up noticibly, but the microstuttering drove me crazy and I went back to 2 GPUs.

You'll be happier with 2 780s, the 1000w power supply should be just fine.

Also, the 800 series is coming out in a few weeks. I wouldn't buy any GPUs before then. Just wait and see what they offer.

 

[byza]

Here is an idea of what you will get at 4K with various card set-ups. The first link has triple monitors and 4K, the second link only has 4K but you can still use it to get an idea of how they compare. Triple monitors seems to be a little easier that 4K.
http://uk.hardware.info/reviews/5419/11/nvidia-geforce-gtx-titan-z-sli-review-incl-tones-tizair-system-benchmarks-bioshock-infinite
http://uk.hardware.info/reviews/4632/7/geforce-gtx-700-series-sli-review-geforce-gtx-760770780-in-sli-and-3-way-sli-battlefield-3---5760x1080-+-frametimes