Sli Compatibility with a GTX 280/260

[logitech30006]

I have an old blackbird that originally ran 2 gtx 280's factory but one went out recently, a friend of mine gave me a GTX 260 he had laying around now I'm wondering if I could run these together or must I have another 280?
I assume you can't considering they both use different drivers. However Ive done about 100 google searches and couldn't find the answer to this.

PS I'm looking to upgrade to a gtx 970 within the next few months possibly, is this the best card I can get for 350?

 

[boosted1g]

Yes the 970 is the best card you can get for $350 and a pretty good deal at that.
You cant SLI two different cards, so a 260 and a 280 will not SLI together.

 

[logitech30006]

Yes the 970 is the best card you can get for $350 and a pretty good deal at that.
You cant SLI two different cards, so a 260 and a 280 will not SLI together.

Straight forward, thank you.