If signal is an issue, then I wouldn't suggest using N. The RF waves are much more susceptible to absorption by walls and other objects.
This is the 5Ghz vs 2.4GHz thing. On 2.4 GHz 'N' actually provides far better throughput/range through walls than 2.4Ghz 'G'.
If you are happy with you current setup there's no need to go out of your way to upgrade though, most 'G' connections are bottle-necked by your home internet speed, so it's only if you stream HD movies or take large file backups between computers in your house that you'd notice any improvement.