I am one who loves eye candy and notice Playing some newer titles I have had to pushing some settings back in order to play.Games like Dead space 3 , Dying light, Assassin creed.. ect I run mostly FPS games. I'm currently running a 27" 1080p 1920 x 1080 res on my monitor and at this time not looking to up grade that part till prices drop. My question here is I see the 970 are great for price but will this be a huge upgrade from my 580? I was thinking of buying one now and using one of my 580 as a physx card when needed in those games. I really don't care about heat or power hungry concerns issues.  I don't have a huge budget I can go about $500 to a 980 but I heard are not worth the extra $$ per performance in not running hi res is this correct?
 
I guess what Im asking is I want to buy a card that will last me 2-3 yrs in gaming and I can always go sli too but stay in the 500 budeget maybe a little more. What are your opinion on this I love to hear all.
Rest of my rig is
SLI GTX Evga 580
MB asus Rampage Gen
i7 3930k
12 gb ram
1200 watt PSU
 
Thanks everyone in advance.
 

Thanks. In your opinion will it last for a couple of years?

Yes you right. Ive had my set up for 2.5 years now. Fun to upgrade but the cost is high. Ive always told my self that this is a hobby and hobbies can be expensive. Thanks again for your input.