Except that you can buy at a very cheap price, do not buy anything that is not current. That is to say 8th generation Coffee Lake of Intel or Ryzen of AMD.
The price of the I5-6600 indicated is very expensive. The equivalent processor in eighth generation of Intel would be the I3-8100 that costs 105 eur.
In addition the I5-6600 uses, as they have said previously, DDR3L memory and, anyway it is a bit fair to treat your card and do streaming.
The I7-8700K is too powerful, it is a waste for your graphic card.
The options I would say are:
On Intel I5-8400 + any mobo B360
In AMD Ryzen 5 1600x + any mobo B350 (Ryzen 5 1600 if you like overclock)
it would be a little better Ryzen 5 2600 + any mobo B350, but then you should make sure that the bios of the mobo is up to date.
If you choose Intel you need DDR4 memory with speed 2666 or higher.
If you choose AMD you need DDR4 memory preferably with speed 3000 or 3200 (although you can run with speed 2666)
The options equivalent to an I5-6600 (somewhat lower than what I recommend) would be an I3-8100 or a Ryzen 5 1500x that could treat the graphics card without problems, but perhaps they would lack something for streaming.
In general, the Intel option is a bit better for games but this advantage is reversed by the fact that you want to stream.