first of all, where did you manage to get that image of your network layout, secondly, check this out...
go to pingtest.net and run a test...
mine is...
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i recommend using CAT6, since the Augmented versions require one end to be grounded and are really only useful for runs over 10 meters, CAT6 will greatly reduce your performance issues, and you can get it cheap from
NeweggUsing your Power-line and Coax converters to network would only be useful on PC's and such since they are rather new to the world of networking above 20Mbps, and a lot of jitter will come from the Power-line because of the dirty electricity (static noise from generators etc) unless you invest in Power-line filters to keep a clean steady flow of electricity you will most certainly see lag from the Power-line adapters. as for the Coax networking, again that's useful for really really long distances, but for home networking i would suggest it.
Coaxial networking i'd consider a last resort if my CAT6 isn't capable then i'd try the spool of CATV 18 AWG i have in my closet. but CAT6 goes for darn near forever, especially with home networking.
your data hub, it wouldn't happen to be a standard Switch now would it, cuz if so, i honestly do not know how you are getting connected to the internet simultaneously, i suggest a router without Wifi then go to a switch and then convert a router into an AP, since that is much more cost efficient way to extend your wireless network.
you still awake?
CAT5e as with any CAT5 cables doesn't have the Gigabit capacity, having the bigger piping would allow for easier communication between your devices, i rarely peak past 104Mbps with internet transfers, but between computers on the network, i sometimes hit around 500Mbps. However i reserve myself for the possibility that CAT# will eventually mean as much as a penny at BestBuy. since i seen information somewhere saying that CAT5 is faster than CAT6... which i think is complete nonsense... but to each their own opinion, right?
The DGL-4500 ever since the 1.20NA update has had major Wifi issues, using an adapted Wireless router for Wifi only on your network will improve the DGL-4500's performance with your network, i know this from experience, i had shut off the wifi for a week and was up for a week. when it was handling both LAN and WLAN it would lock up and freeze 2 times a day on a good day. you jitter and latency issues will almost disappear when you manage these changes.
as for your pinout, be sure you are using a proper pinout by regulation. i use the T568B Gigabit pinout for my entire network. When using a pinout, do not put the same cable with different pinouts, such as, a T568A on a patch cable that leads to T568B, you might get some connectivity but there would most definitely be no connection if any connection it would be outrageous in lag, jitter, etc.
CAT6 pinouts for the information pertaining to proper pinouts.
i hope this helps, and i hope your head didn't explode with this bombardment of information, if you have further questions i'm sure many of us here can help, i'm speaking mostly from personal experience, and stuff i've learned over time. I once was interested in either Coax or Power-line networking, but was turned away from the latencies and jitter of both.