Buy Used on Ebay or New?5

There seems to be some good prices on old Dell XPS 8500 models i7 3770 8gb RAM 1 TB HDD PSU I believe to be 300W These models usually sell for around $250 to $350, figured I could throw a gtx 1050 ti and play some games on it. Could I buy a better system new for under $500 that easily beats the performance of that? If you plan on upgrading over time, OEM PCs like the Dell can be a bit troublesome.