Question computer getting slower speeds compared to other devices around the house

[DJQuik]

we've recently upgraded our internet service to gigabit and i've noticed that every other device is getting much higher speeds in the hundreds, meanwhile my personal computer maxes out at 15 mbps and might hit 20 mbps occasionally. i'm wired through powerline ethernet and also have wireless capabilities through a rosewill rnx-ac19000pcev2 i had installed recently, both are getting the same speeds. i even wired it through a wireless linksys range extender and got the exact same speeds, meanwhile i was able to wire it into our mac in the next room and it had speeds in the hundreds once again. i've tried everything under the sun to increase the speeds but haven't had any luck.

(relevant?) hardware is as follows:

MSI Z370 SLI PLUS
INTEL i7 8700K
ROSEWILL RNX-AC19000PCEV2

 

[SamirD]

Try wiring directly to the router somehow (or is that what you tried when you wired it to the mac?). If you don't get the same speeds, then we have to diagnose further.