Alienware Aurora running worst than x51?

My Aurora's specs.

Win 10 64bit

8GB Ram

Intel i7-6700

AMD Radeon (TM) RX 480

I bought this PC shortly after my old Alienware x51 suddenly died and could not be fixed. I had it for 3 years and it could run completely fine and handled almost every game perfectly on very high graphical settings. I now have an Aurora. The Aurora cost about 1400$ while the x51 cost only around 800-900$ if my memory is correct. Every since I've gotten the Aurora its been giving me problems. In a supposed system update one day without any warning it wiped the entire PC back to factory default. However ever since I've gotten it I've noticed one very big difference. A game that I play very often, that is not very hard graphically is almost unplayable at times unless if its on the lowest settings. This is the same with various other games. This game could be run on high graphics by most office laptops and so I can't understand why a thousand dollar gaming PC has a struggle to run on medium in some cases. I've made sure to keep my graphics card up to date and it can't be the memory as this was a problem even when the PC was brand new. 

I would like a little insight into possible causes and what I could do to fix this as I would like to be able to play above the minimum graphics settings on a PC built for gaming.