The main problem is the interference. Speakers, TV, kitchen equiptment, other electronical equptment and so on will make an intereference and lower to signal strenght and stability.
At least for the small places I have lived in, it's just too much stuff on small places that screws up the signal for me. Tried with more than a router and the results is allways the same - not any near as good as cabled.
in my uni flat there were two walls, one chimney, one bathtub and one boiler in the direct path (~7 meters) between router and my computer, and I still got 80% receiving power. But my wifi card had a rather big external antenna.
Yes, more power usually will not help with WLAN interference/signal issues. It sounds like you may be suffering from phase cancellation. That is, the signal is being reflected, and the reflection cancels out the actual signal due to being out of phase. Increasing power will not likely help. Also, those reflections will reach the device as well. So you have the main signal, and then all of the reflections of the signal arriving way out of phase with eachother. More power means the reflections are also more powerful so this just raises the noise floor. Also, no matter how high you set the Tx power on the AP, your laptop/other devices are still going to be transmitting at the same power level so it's pointless anyway.
Ugh... I think I said wrong sorry hehe.
What I meant is that I have tried with different routers, not more routers at same time or done any technically changes to them or the computer. I did however try the different frequenze channels on the router(s) without the big effect changes.
Same but I use EE-2 wifi. Never had a problem with wireless since I started using it I can access through my phone the wi-fi from about 30 meters away outside in the street.