Buy used gpu isn't reliable for me. I think beter was to buy new with guarantee.The build is a modern one, although, me personally, I am a big fan of repurposing older corporate machines for everyday use and buying used GPUs. You could have probably got a more powerful GPU ( these days I just bought a 4GB RX 480 for 100 cad ).
Lately I prefer my systems to have a fast boot drive, 250/500 GB SSD, with an external drive on usb 3.0 for mass storage, presently I have a 4 TB portable drive.
It is really debatable how much computing power a home user really needs but in general an older Core i5 does the trick. You have a hex core system, a solid foundation, that will allow easy expansion in case you feel you will need it! Your next upgrade target should be the SSD, it will make the system so much faster.