When we tested the Core i5-6400, we concluded that it was a good CPU for work and gaming but, due to its low clock, had a performance too close to the Core i3-6100, which costs a lot less.
We imagined that the Core i5-6500, with its 18.5% higher base clock (3.2 GHz vs. 2.7 GHz), could deliver a better cost/performance ratio. However, on real world, the performance increase was small, and as the Core i5-6500 costs a little more, the cost/performance ratio was pretty much the same of the Core i5-6400.
Anyway, the Core i5-6500 is a good CPU for an intermediate work or gaming PC. However, if your priority is keep the low cost, the Core i3-6100 is still a more interesting option. On the other hand, if you need CPU multi-task performance, the Core i7-6700K is a better deal.