I'm leaning towards an Asus Nvidia GeForce GTX 970 Strix 4GB (link) and a Corsair Builder Series CXM 750W PSU (link).
Now my PC is very old but does the job so far, and whilst I can throw a few hundred quid at it, I don't want to go down the new PC route at this time, its a Dell with a Core 2 Quad CPU Q9550 2.83GHz (don't laugh at me

So two questions for those tech savvy, from this poor computer idiot...

1) will this all work, or am I living in a dream world?
2) is there anything I need to think about beyond simply plugging it all in and hoping for the best?