First, a warning that you are getting into the area of diminishing returns, money spent doesn't guarantee a significant improvement in performance.
For overclocking to a level above the 1231 so you will want an Intel CPU, AMD doesn't make it at this level. Maybe someday soon.
I believe your best option here is to go with the Haswell-e i7 5820k and an X99 motherboard. This will handle the multiple GPU well and give you some decent overclocking headroom. The PSU and the memory will have to go though, they won't cut it. Below is my suggested build where I tried to salvage the components from current build, 6 months old is not that old. The extra video card is included just to show that it will work. I also bumped up the CPU cooler to the NZXT Kraken X61 since you are now getting into the area of extreme demand (hey, you didn't give me a budget
).
PCPartPicker part list:
http://pcpartpicker.com/p/GMHZ6h
Price breakdown by merchant: http://pcpartpicker.com/p/GMHZ6h/by_merchant/
CPU: Intel Core i7-5820K 3.3GHz 6-Core Processor ($374.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.88 @ OutletPC)
Motherboard: ASRock X99 Extreme6 ATX LGA2011-3 Motherboard ($213.98 @ Newegg)
Memory: G.Skill Ripjaws 4 Series 16GB (2 x 8GB) DDR4-3000 Memory ($89.99 @ Newegg)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive ($87.89 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.98 @ OutletPC)
Video Card: Asus GeForce GTX 970 4GB STRIX Video Card (2-Way SLI) ($308.49 @ SuperBiiz)
Video Card: Asus GeForce GTX 970 4GB STRIX Video Card (2-Way SLI) ($308.49 @ SuperBiiz)
Case: NZXT H440 (Black/Red) ATX Mid Tower Case ($118.99 @ SuperBiiz)
Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($117.99 @ NCIX US)
Operating System: Microsoft Windows 8.1 OEM (64-bit) ($89.95 @ OutletPC)
Keyboard: Corsair Raptor K30 Wired Gaming Keyboard ($79.99 @ B&H)
Mouse: Corsair Raptor M45 Wired Optical Mouse ($58.23 @ Amazon)
Total: $1923.84
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-01-18 17:04 EST-0500