New to upgrading computers and want to SLI my GTX 670

[Vonixzee]

I am considering upgrading my rig because new games are coming out and its falling behind, I'm new to this kind of stuff so what I want to do is SLI My Asus Geforce GTX 670 mini with another GTX 670 card, but I'm not sure if I can. I cannot find any of my card type on Ebay or any other sites and also do not know if my rig is compatible with this either.

Specs
Case: Cooler Master Haf 912 (not sure if it will fit sli)
Motherboard: Asus Z87-A (Upgrading from my Z87-C so I can have sli support)
Processor: Intel i7 4770 3.4GHz
Ram: 8gb DDR3
Graphics Card: ASUS GeForce® GTX 670 DC Mini
Hard Drive: 2tb (all I know is it is 2tb if needed I will find out what type)
If anything else I haven't noted isn't here please tell me and I will try and get the information
Thank you

 

[Alpha3031]

Don't bother. I'd just get a single new card, either the R9 290 or a GTX 970. Make sure your power supply is large enough though.

 

[Vonixzee]

Don't bother. I'd just get a single new card, either the R9 290 or a GTX 970. Make sure your power supply is large enough though.

That will probably be allot easier but wouldn't it cost more because I have a spending range of $450

 

[Alpha3031]

Then both the cards mentioned will be easily accessible, and probably better for gamed requiring lots of VRAM.

 

[Vonixzee]

Okay thankyou very much I'll get a gtx 970