^ that was tricky to figure out. took me a second or two to understand that Snipergod87 was talking about me
anyway, I have an old TP-link router (don't remember how I got it. I keep it as replacement if something happens to the main gear) that has only 100Mbps lan port. I used it for a month or so couple of years ago and if i was transferring file/files on network (PC and NAS for example) everything else like browsing internet would halt.
Even expensive toys like my RT-AC68 have their own performance issues. 2.4Ghz Wi-Fi and USB port were using same CPU resource. So the HDD connected to the router would work only at ~30MBps instead of ~70MBps if the 2.4GHz is enabled. I solved it by overclocking the router CPU from 800Mhz to 1000Mhz. it actually worked at 1.2GHz but at relatively high temps. Doubt many users will do that to their router.