No one is going to judge you for bying a pre-built welcome to the forum. What matters most in a GPU upgrade is the power supply and many times those vendors include a sub-par PSU it's usually just enough to run what you have. If you can list the power supply unit you have in your unit. If you will take the side cover off usually there is an affixed label with the specifications. Post a pic here, or just tell us what it says (brand/model.wattage) and the +12v ratings you can see. If you are also looking to upgrade to a new or better CPU the motherboard matters. From what I can see here_http://www.newegg.com/Product/Product.aspx?Item=N82E16883272146 - and with the pic of what may be your board here
Looks like you likely have a lower quality Ultra 500W PSU and an MSI 760g mobo. Probably the P23 or P34. Let us know what you intend to do with your PC going forward. If it's a CPU upgrade (if you have that same mobo) I would not upgrade to anything past a FX 6300 and maybe a RX 470/GTX 1060, but for sure if I di that I would upgrade to a better quality power supply unit something like a Seasonic 520w-eVGA 600w.
Edited by Zone_86, 03 December 2016 - 07:26 AM.