System Built - Should I Upgrade Mobo / Proc?

I have the following system specs picked out for a buddy. What I'm wondering is should I wait until the processor comes in stock to get the better Sandy Bridge and motherboard with 2 PCI-e slots @ 16x, in case he wants to Xfire the 7970s a year or so down the road?

-How much better gaming performance will he see from the better processor?
-How much better gaming performance will he get out of the PCI-e slots both running @ 16x on the other mobo if he decides to xfire?
-Also any potential recommendations / suggestions about the build in general?

**He has a 1TB external HDD for storage.


Here are the current system specs:

Case:
COOLER MASTER HAF 932 Advanced RC-932-KKN5-GP Steel ATX Full Tower Computer Case with USB 3.0, Black - http://www.newegg.com/Product/Prod [...] 6811119160

Vid Card:
XFX FX-797A-TNBC Radeon HD 7970 3GB 384-bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card - http://www.newegg.com/Product/Prod [...] 6814150591

RAM:
G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBRL - http://www.newegg.com/Product/Prod [...] 6820231314

Mobo:
ASUS Maximus IV Gene-Z/GEN3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard - http://www.newegg.com/Product/Prod [...] 6813131806

Processor:
Intel Core i7-2600K Sandy Bridge 3.4GHz (3.8GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 - http://www.newegg.com/Product/Prod [...] 6819115070

Power Supply:
CORSAIR Professional Series HX1050 1050W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS SILVER Certified Modular Power ... - http://www.newegg.com/Product/Prod [...] 6817139034

SSD:
Intel 520 Series Cherryville SSDSC2CW120A3K5 2.5" 120GB SATA III MLC Internal Solid State Drive (SSD) - http://www.newegg.com/Product/Prod [...] 6820167093


And here are the 2 potential replacement candidates:

Processor:
Intel Core i7-3930K Sandy Bridge-E 3.2GHz (3.8GHz Turbo) LGA 2011 130W Six-Core Desktop Processor - http://www.newegg.com/Product/Prod [...] 6819116492

Mobo:
ASUS Sabertooth X79 LGA 2011 Intel X79 SATA 6Gb/s USB 3.0 ATX Intel Motherboard - http://www.newegg.com/Product/Prod [...] 6813131801

the difference between the 2600K and the 3930K in actual performance is not worth the huge pricetag difference.

on a single 1080p monitor, crossfire of HD 7970s is overkill in the extreme. everything you throw at a single card will exceed 60 FPS

the gen 3 in your existing board means it'll handle the crossfire at pretty much full speed.

Previous testing shows, at least under PCIe 2.1, the difference between 16x/16x and 8x/8x in Crossfire or SLI is about 2%.

This means if 16/16 gets 100 FPS, 8/8 gets 98 fps. it's not really noticeable.

that said, by the time you'd want to crossfire a 7970 for any actual practical reason, iit'll be smarter to build a whole PC instead.