I have an old laptop (which is definitely on its last strides). It's a MacBook Air Late 2010 and its running like a slug (I have abused the laptop beyond comprehension) so for its final year or two I want to get the most out of it. I already have a 2' monitor attached and I want to know if I get a GTX 970 and attach it with one of these things (Using thunderbolt) if it will function properly and that I'm not burning $600 for something my computer can't handle.
Unfortunately not, your Macbook doesn't have Thunderbolt, only Mini DisplayPort. For best results, your mac should have Thunderbolt 2 to take full advantage of the speeds.
By the way, I have Macbook 2011 and I had 2x Thunderbolt displays at 2560x1440 with my integrated HD3000 512mb without a problem. But it was fast as hell when I added a SATA3 SSD with 560mbps read. Hard drives are bottlenecking! :)