Yes you can boost the signal strength but only at the cost of more power consumption.... lol which intern means heating up of chip which if ur not care full you can burn it.
But still if your in safe limits you can still enjoy lots of things....
Lynksis had made its firmware open source after which there are many 3rd party firmwares developed. You do get lots of features inside other than stock.
Now if your buying WRT54 be carefull, in India you get Ver7 which has lower memory and third party firmware cannot be flashed. However there is a lighter version of the firmware with strip down features which is also cool.