Should I upgrade my Plex server to a Xeon E3 or i7 CPU?

I am looking to upgrade my system to something more powerful. Right now i am running a i3-2120 PC (Passmark score of 3886) with several external hard drives. I constantly have between 6-8 streams daily (9 streams recently for the first time) with many of those streams transcoding (720p max). I feel like this system gets sluggish, although I am not too sure how to tell if its my system or the streams themselves (bad wifi or problems at the users end and not mine).

My questions are the following…

1 - How would I tell if its my server which is stressing out the streams or the user’s system? I have PlexPy running in the background and I can see certain times people might need to restart their stream or some buffering randomly occurs.

2 - If its time to upgrade my system. Should I upgrade to a Xeon E3-1230 v5 or an i7 (6700k or some other chip)? Which would be best for maximum transcoding streams?

Perhaps I should have certain settings enabled/disabled as well.

The most important thing with the CPU is single stream processing, so when you search for a CPU and you look at the passmark score, don’t just compare the overall result, look at the single stream, because that is what Plex uses for transcoding.