High Powered Wireless Network for Audio

You should go to the Linksys website for a complete tutorial. I had difficulty getting a wireless signal from one side of my house to the other, so what I did was get 2 routers, one for each side connected by a wire with the routing function disabled on the second router, turning it into a switch with wireless access point. I gave both routers the same SSID so my computer(s) could choose the one with the best signal depending on location. I tried a range expander but that made things worse, I think by creating reflections that were difficult to discern. Be mindful that any and all wireless devices share 1 port, whereas each wired device gets the port it's plugged into. So if you had 4 computers plugged in to ports 1-4 and a 4 computers wireless , each wired port gets 20% (1/5th) of the "signal" and each wireless computers gets 1/4 of the remaining 20% allotted to the wireless access. With my setup, I have 2 access points, so not as much competition for "air time".

Your router may be just getting tired. I had an access point that seemed to put out less signal as it aged. I went with 2 access points because I have a lot of foil faced insulation in my house as well as duct work which I think created shields. The line of sight from my den to my patio is completely blocked by my house causing occasional dropouts. Placing the router in the center of the house was also not a great option for me.
Whatever router you choose, I would recommend the gigabit ethernet variety (10/100/1000) as opposed to an N router that only does 10/100. Linksys makes 2 types of dual band models, one where you choose either high or low band and use only one band at a time, and another that puts out 2 bands at the same time. BTW-the bands have nothing to with channels. You would still choose the channel for each band with the less interference.