Motherboard and CPU, yes, they will make a big difference. The RAM? No, you'll never notice even a slight performance difference. Complete waste. I'd rather swap that 560 Ti for a 570. 
EDIT: Oh, missed that you're going from 4GB to 8GB. But even then you won't get any noticeable performance increase out of it. If you have a SSD system disk it does make sense since you can disable page file, create RAM disks etc..
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn!
"The sky was the color of a TV tuned to a dead station" - Neuromancer
Motherboard is great though 
