As you have a GPU, CPU only, the fastest and unlock is the Athlon X4 760K for overclocking, if you don't need it unlocked, Athlon X4 750, but check prices as, FM2+ is end of life and you could get a good deal on a "K" model and not bother overclocking.
On the other had, you could go with one of the A series APUS, whose integrated video can be twice as fas as your GT730 and get a 6870K,6790K,5800K,6700,5700 in order of performance.
I have a A10-5800K APU in a HTPC and never bothered overlcocking and at a push can just about managed 4K streaming, but 1080 streaming is smooth.