Crossfire 7870's?

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Hi all, I'm thinking of getting a 2nd Gigabyte 7870 to run in crossfire with the one I already have. I have seen them online for about £150 new and this seems to me like a good option. Just wanted to know if anyone out there knows if there may be any problems with me doing this on my system (below), if the microstutter is still a problem or if there is any other options to get similar performance without it costing much more.

Thanks.

My system;

CASE - Cooler Master CM690ii Advance Black and White Edition
MOBO - Gigabyte GA-Z77-DS3H
CPU - Intel Core i5-3570K
CPU FAN - Cooler Master Hyper Evo
RAM - Kingston HyperX DDR3 1600MHz CL9 16GB (4x4GB)
HDD - Seagate Barracuda 1TB 3.5" SATA-III 7200RPM 64MB Cache
GPU - Gigabyte AMD Radeon HD 7870 2GB
PSU - Cooler Master GX Lite 700w
OS - Microsoft Windows 7 Home Premium 64GB
KB - Cooler Master Quick Fire TK CHerry MX Blue's
Mouse - Sharkoon Drakonia Mouse
Monitor - BenQ XL2411T 24" 1080p, 144hz LED Monitor

 

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Ok thanks, I diddnt realise about the PCIE x4 speed thingy, i'm pretty new to PC's. Thanks for the help

 

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Thanks, I'll definitely take a look at the new GPU's before deciding what to do. As an afterthought is it worth overclocking my existing 7870? I mean would I see a noticeable improvement in performance and would I need to buy a better aftermarket cooler than the stock one?

Thanks again guys

 

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"The R9 280X is priced at $299" wow that's roughly £185 before VAT. What kind of increase in performance could I expect from that card over my 7870? Also what would be the Nvidia equivalent performance wise to the R9 280X?

 

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Also I've heard that the R9 280X is pretty much a re-branded 7970 so if it works out cheaper wouldn't it make more sense just to go with the older 7970?