Need to narrow down if it's the router or something else causing your lag first off before trying a different router.
What ISP Service do you have? Cable or DSL?
What ISP Modem do you have? Stand Alone or built in router?
What ISP Modem make and model do you have?
If this modem has a built in router, it's best to bridge the modem. Having 2 routers on the same line can cause connection problems.
Double NATTo tell if the modem is bridged or not, look at the routers web page, Status/Device Info/Wan Section, if there is a 192.168.0.# address in the WAN IP address field, then the modem is not bridged.
If the modem can't be bridged then see if the modem has a DMZ option and input the IP address the router gets from the modem and put that into the modems DMZ.
If your on Cable, please ensure the signal going into the ISP modem is good and at spec for the modem. Have the ISP check there lines and any log information. Using t.v. line splitters can effect signal going into the cable modem. Garbage In, Garbage Out. If your on DSL, ensure the phone lines are the same as cable, signal is good and lines are filtered where needed.
I would check in game performance with you PC directly connected to the ISP modem.
Turn off all anti virus and firewall programs on PC while testing. 3rd party firewalls are not generally needed when using routers as they are effective on blocking malicious inbound traffic.
Turn off all devices accept for one wired PC while testing.