Prebuilt computers are awful. Never buy one. Ever. You can literally build a more powerful computer for the same price, sometimes you'll even save money too.
Yep, this is true.
I built my computer for only 700$ using an I5-4690K, an 120$ Mobo, 16GB of nice ram, a GTX 970, a Fractal Design Nano S, a Seasonic M12II 620 Watt Fully Modular PSU, good thermal paste, a Cryorig H7 CPU cooler, 3 Fractal Design case fans, Windows, a Keyboard, and a Mouse. I had a monitor already, so that was taken care of.
The GTX 970 was more recent at the time, but I've overclocked it to GTX 980 levels.
Far cheaper with arguably higher quality parts when it comes to the PSU and CPU cooler than it ever would have been if I had gotten a prebuilt computer. I was able to make use of a lot of sales and snagging new parts on Ebay to bring the price down even further. If I had skimped on some things like the case, I could have shaved off even more from the price.
Now, can a prebuilt computer preform well? Yes it can, but you are still overpaying massively for what you get. If you bought a prebuilt computer for 1000$, for that same price you could build a far more powerful computer if you did it yourself. You will also have more control over what's in the computer in regards to hardware, which includes the quality of the parts you choose to buy.
There is a reason the prebuilt PC market has been in decline for years now.