Hello. It depends to be honest. I prefer Intel so I'd go with a Intel Core i3-6100 3.7GHz. Although it is a dual-core, it has got hyper-threading which means every physical core has 2 logistic cores so it has 4 threads altogether. It would do the job for the multi-tasking in my opinion as well as streaming.
Now for another option (AMD) I'd pick AMD FX-8320 3.5GHz. It is a 8-core. I think AMD cores are weaker but this CPU would do the job for what you want in my opinion.
Here are the links:
Intel i3-6100 3.7 GHz :
http://pcpartpicker.com/part/intel-cpu-bx80662i36100 (129,89$)
AMD FX-8320 3.5 GHz :
http://pcpartpicker.com/part/amd-cpu-fd8320frhkbox (129,99$)
Good luck!