A different router can affect your latency, but don't expect a night and day difference. In the EQ era, Linksys released a firmware update that totally hosed playing EQ. This was during a time when SOE was trying to secure their data stream so that application like ShowEQ wouldn't be able to intercept and decode the data transmitted to the game client. SOE's new secure data stream ended up causing certain Linksys routers to shutdown as they interpreted the EQ data stream as a type of DOS attack.

There have been other instances of routers not dealing well with constant streams of data, but I have not heard of any major issues in the last 5 years. Most of the home/SOHO routers have matured quite a lot and provide very good throughput. There are some specific routers aimed at gamers which utilize QOS metering to give priority to UDP and other types of "gaming" traffic. Even these will only provide a marginal increase in performance. The most important factor of latency is going to be your ISP.

Go visit www.dslreport.com. You can run a variety of tests through their website and see if your latency is typical for other users of your ISP in your area. This should show you if your getting typical results or if there might be a problem.