new build for 3d modeling and rendering

Support Technical Support
1

Hi!

I am trying to put together a new system and would kindly appreciate any feedback on what I have chosen. I still haven’t made up my mind on a few aspects like whether go with 16GB of ram for the time being and get more later or just get 32GB on the start. Then I dunno whether I should go for Windows 8 or 7. And lastly the GPU/GPUs - what’s better? Two cards would mean I can use rendered view in cycles and avoid any lags so I guess this is something I should go for.
What do you think?

------------ Case
Fractal Design Define R4, Various, Steel/Plastic, 232x523x464 (WxHxD in mm), 2x USB 3, 2x USB2, Headphone & Mic - 79.68
------------ Motherboard
Asus Z97-Pro WiFi AC, SLI, CrossFireX, 4 SATA 6Gbps, 1 SATA Express, 1 PCI-E M.2, SATA RAID, WiFi, Bluetooth, ATX - 161.69
------------ CPU
Intel Core i7 4770K, Haswell, Unlocked, 3.5GHz Quad Core with Hyperthreading, Retail (overclocked to 4.2) - 245
------------ Cooler
Noctua NH-U14S Ultra-Quiet Air CPU Cooler - 59.59
------------ VRAM
16GB (2x8GB) Corsair Vengeance Pro, 2133MHz, CAS 11-11-11-27, 1.5V - 131.52

or

32GB (4x8GB) Corsair Vengeance Pro, 2133MHz, CAS 11-11-11-27, 1.5V - 263.04
------------ GPUs
EVGA GeForce GTX 780 6GB SC w/ EVGA ACX Cooler x2 - 680 (seems a little cheap after conversion from dolars - not yet on scan.co.uk)

or

6GB EVGA GTX Titan Black SC, 967MHz GPU, 2880 Cores, 7000MHz GDDR5 - 863.75

or

GeForce GTX 780Ti 6GB x2 (when they are out) -??(a little more than titan?)
------------ PSU
750W Corsair RM, Modular, Silent, 80PLUS Gold - 89.70

or

1000W Corsair RM, Modular, Silent, 80PLUS Gold - 142.92
------------ Drives
250GB Samsung 840 EVO - 540MB/s Read, 520MB/s Write, 97K IOPS - 113.81

1TB Seagate Barracuda, 7200rpm, 64MB Cache - 43.18

Samsung SH-224DB - 24x DVD Reader & Writer - 11.98
------------ OS
Microsoft Windows 7 Pro 64bit - 104.48

or

Microsoft Windows 8.1 Pro 64Bit - 98.17
------------ Monitor
27" Dell U2713HM LED IPS, 2560x1440 - 437.12

total ~ 2700

2

Moved from “Misc: > Off-topic Chat” to “Support > Technical Support”

3

It seems like there is nobody willing to give a tip on my build.

And I have yet another dilemma. Most of the Haswell motherboards support only single PCIe x16 bus, which means two graphics cards will have to share it resulting in lower bandwidth available for each card. Only the high end boards have a sort of switch that allows for dual x16.
So my question is: what kind of performance hit are we talking about when using x8/x8 compared to x16/x16?