I have a small i3 Machine which I use for all my dockers and mainly plex and looking to possibly upgrade the Intel i3-4130T to a Xeon CPU. The motherboard is Gigabyte GA-H97N-WIFI and the case will probably only support a stock fan. Any suggestions on a CPU with significant better passmarks?

Here is the supported CPU list for your motherboard. Anything at an i7 or Xeon level with at least four cores will suffice. It really comes down to how many concurrent plex streams you want to be able to support.

 

http://www.gigabyte.com/support-downloads/cpu-support-popup.aspx?pid=4992

 

Also, that board supports Intel integrated graphics so make sure you get a chip that supports it as well (some Xeon's don't).  Since the board doesn't support ECC memory you wouldn't necessarily benefit from a Xeon so Core i5/7 chips should be on your candidate list as well as Xeon.  The Haswell era E3 Xeons are very similar to the similar Core i5/7 chips so you can shop on cores, clock speed, Passmarks and price if you don't need Xeon specific features like ECC.  E5 Xeons are a different story but they won't work on that board.

If you need ECC RAM -> get a different mobo and use Xeon.

If you don't need ECC RAM -> save some £ and get i7 / i5. As tdallen said, E3 Xeons are similar to i5/i7 (I would go so far to say E3 Xeons are basically i7 chips with ECC enabled).

 

You CAN certainly get Xeon and use it with non-ECC but then it would be like driving a Mercedes-Benz G-Class in central London.

I have no need for ECC ram as all my data is actually on another machine and my appdata is backed up weekly. I just want my family to have a better plex experience. I have had a few moments where my brother has called and said the movie has stopped half way or keeps buffering  over WAN.

 

My current CPU has avg. passmark of 4112 so thats should be enough for 1x 1080p 1x 720p transcode?

 

Looking at plexpy I have had a max of 5 simultaneous streams. Mainly TV shows by the looks of it.

 

Something around the 8000 passmark would be probably be more than enough for what I need.

As already noted, since your board doesn't have ECC support there's no real benefit to using a Xeon.  I'd just pop in an i7-4790, which bumps your PassMark up to 10003 ... a nice increase that will eliminate processing power as a factor in your Plex streams.

 

By the way, with the broadband connection you have, it's clearly not likely that internet bandwidth is an issue either 

 

[Your upload speed is well beyond what you need; and your download speed is simply amazing !!]

 

I think thats what I will be doing! Will look on ebay as still quite pricey brand new and yes been quite lucky in the area I live we have always had good cable broadband.