We've got 3 routers (2 are G, 1 is N), 20m and 2 bars is pretty normal.
Goes 25m tops, although on my built in Intel card it can goto 29m. (Line of sight) And with the top of the line D-Link DWA-160 N usb adapter, I got 21m line of sight broadcasting at N. =\ Just getting higher speeds.
In the end I just flashed the firmware of one of my routers, to be used as a repeater. (Just broadcasts what it receives, acts as a signal booster)