Building a new PC and looking for some feedback.

[JaSamHen]

Hi! As stated in the title, I am building a new PC to play the game. Here is my current build:

CPU: AMD Athlon 64 X2 6000+
Motherboard: Asus M2N-SLI Deluxe
Memory: 3GB Corsair DDR2 PC2-6400 (800MHz)
Video Card: AMD Radeon HD 7770 1GB

What I will be building:

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor
Motherboard: ASRock Z97 EXTREME6
Memory: Corsair Dominator GT 16GB DDR3-2133 Memory
Storage: Samsung 850 Pro 256GB 2.5" Solid State Drive
Video Card: GeForce GTX 970 4GB 256-Bit GDDR5 PCI Express

My question is will I see a significant improvement? The game is playable now, but really bogs down when in populated areas (less than 10 FPS). It also utilizes 100% of my CPU while playing, regardless of location. I'm also curious as to feedback regarding which GTX 970 to purchase. I've read reviews on several and feel that the Gigabyte version might be the one to go with, but would like other opinions if possible. Thanks for your time.