Probably the radio in the wireless router is starting to degrade and will eventually fail.
You'll definitely want to have dual band capability. More specifically, you'll want to have 5 GHz capability as there are more available channels and less interference (currently) which will translate into more reliable connections and better performance.
In the SOHO arena of wireless routers, many of them are pretty much the same. The ones which tend to get a decent following are Linksys, Asus, and Netgear. I can't recommend one personally to you as I haven't looked at SOHO class equipment for many years. I've moved on to business class equipment for my home network.
A good place to check out reviews on SOHO wireless routers is
http://www.smallnetbuilder.com/