Wireless isn't supposed to have a massive range, so changing routers might well not solve the problem.
Changing router location, might be more beneficial, but probably impractical.
Some routers do allow third party firmware which adds controls that mean you can increase the signal strength. Who knows whether that might be detrimental to your future health and sperm count
so probably not a good idea.
That leaves two alternatives. Adding the signal repeater, as indicated above (cost benefits, only the one bit of kit too add / change), or looking at an alternative networking solution such as the LAN over power supply systems, Homeplug I think it's called (cost may be high as lots of things need to change or be added).