I have a Windows XP system that isn't able to play the high end games so I'm going to buy another one.
I use my PC for other things besides games though.
For example, I enjoy taking 4K nature videos and playing them on my PC.

I found a PC that is "high end"

Dell - XPS Desktop - Intel Core i7 - 16GB Memory - 1TB Hard Drive - NVIDIA GeForce GT 730 2GB dedicated graphics

Best Buy has it's own category of "Gaming Desktop" and this isn't one of them. I've noticed that "Gaming Desktops" are a little more pricey than others. Is this just a gimmick?

You shouldn't use these 2 things in 1 sentence. O.o

+ How much do you know about / are you interested in computers?
+ How much do you want to spend?
+ What games do you want to play?

If you don't want to build your own a computer, a gaming premase pc is a good option, but google the specs. That RAM and CPU seem fine, but the GPU seems to be pretty shite. At least for gaming.

The GPU of that PC is rather useless.Not much better than the integrated one. Also, you probably want an SSD instead of just a hard drive. Or maybe in addition to one.
Although CPUs called "Intel Core i7" are usually reasonably fast, that information doesn't say anything about which CPU generation that is. When buying a new computer, you usually want components from the current generation (in case of the CPU that would be an i7 of the Skylake generation, e.g. an i7-6700 ) unless you have a good reason for buying older stuff.
When it comes to gaming an i7 is usually not necessary. An i5 will do just fine and can save you some money which you could use to buy a better GPU. An AMD Radeon RX470 for example would be a very decent gaming GPU for about $200.