Rate my new rig

I just recently bought a Dell XPS 8900 Special Edition and figured I wold upgrade the stock GPU (R9 370) with a GTX 970. However I also had to get a new PSU to support the new GPU and figured I'd buy the highest wattage they had, because I had the money so why not. But, it seems like my computer is running slowly, so I figured I'd just ask for some help from some people who know what they are doing. I really only plan to use this rig for gaming and Netflix.

PSU: Corsair 850W
CPU: Intel Skylake i7-6700 @ 3.41 GHz (stock)
RAM: 16.0 GB DDR4 @~1064 MHz(stock)
GPU: Geforce GTX 970 4GB GDDR5
HDD: Seagate Barracuda XT 2 TB (stock)
OS: Windows 10 Professional (64-bit)