I got the same deal. Although it's quite a low spec the base of the system (MB and PSU) can cope with up-to at least a R7 1700X , GTX1060 and 16GB DDR4.
My immediate plan is to throw in a 128GB SSD from my old system and have some 1080p gaming fun for a few months, then I'll sell the R3 and RX560 and swap in a R7, GTX1060, 8GB more RAM (probably cost like £400 net the same of the other bits).