IPC is short for instructions per clock, for example if two CPU's have the same clock speed but one has a 5% higher IPC then you will get 5% better performance from the CPU with the higher IPC. As said cores don't really matter that much for gaming past 4/6 and with the great value of the 2600 I'd get that.


Edit: gaming performance benchmarks of R5 2600 vs R7 1700
https://www.youtube.com/watch?v=_2WVFK0V-Vc