That CPU IS strong enough for some use with video rendering and editing, but clearly something with more cores/threads would certainly be a huge benefit in that area. Also, you are hampered by having 6GB of RAM.
Not just because its a rather low amount, but also because with an oddball number like that it can not be operating in dual channel. You need sets of two or four sticks in amounts of 1 x2GB, 2 x4GB, 2 x8GB, 4 x4GB or 4 x8GB, etc, for dual channel operation and that will double the bandwith of the memory which can show a nice increase in performance especially in non-gaming applications.
https://en.wikipedia.org/wiki/Multi-channel_memory_architecture
Your biggest setback to upgrading may actually be your case. Clearly your GPU card is too low end for the kind of performance required to viably do editing or rendering of 4k video, and being limited to 4 cores, even though they are relatively strong cores, they are 4 almost five year old cores.
I'd suggest that perhaps an upgrade to a Haswell i7 plus a fairly higher tiered graphics card, or a complete upgrade to an entirely new platform will be required to accomplish the tasks you are looking to do. That might definitely also require the inclusion of a new case to accomodate a larger graphics card, depending on what GPU card dimensions your case can support, and a larger, higher quality power supply as well.
Acer, HP, Dell, these are companies not known for including high quality power supplies with their prebuilt systems and while they might, just barely, be ok for the systems they are included with, they are definitely not adequate for upgraded or gaming systems. You must also consider that watts is not the only determining factor. There are plenty of "600w" units out there that can barely supply 250w, so the quality of the unit is a big factor and just because a unit carries a name like Corsair or Cooler Master does not mean that it is in fact a high quality unit that is capable of long term, high demand use with video or gaming systems.