Is it worth the upgrade for crossfire? (x16, x4 to x16, x16/x8)

Currently, I'm running 2 x HD 6850 IceQ (http://www.newegg.com/Product/Product.aspx?Item=N82E16814161363) in crossfire on a Gigabyte GA 970 UD3+ (http://www.newegg.com/Product/Product.aspx?Item=N82E16813128519) motherboard. I understand I'm running in an x16, x4 configuration due to the motherboard at the moment, and I was wondering if it would be worth the upgrade to ASUS M5A99X EVO AM3+ AMD 990X (http://www.newegg.com/Product/Product.aspx?Item=N82E16813131754), ASRock 990FX Extreme3 AM3+ AMD 990FX (http://www.newegg.com/Product/Product.aspx?Item=N82E16813157281), or just stick with my current mobo if the increase won't be significant. Also, if there are other things that anyone thinks would justify an upgrade to a different motherboard, mention those as well. Thanks in advance!


FULL SYSTEM SPECS:

Case: Coolermaster Storm Scout
Mobo: Gigabyte 970A-UD3+
CPU: AMD x6 1090t @3.6Ghz
CPU Cooler: Coolermaster Hyper 212 Evo
HDD: Seagate Barracuda 1TB 7200RPM
GPU: (2) Radeon HD 6850 IceQ x Turbo 1GB
PSU: Raidmax RX-730SS