Think the issue with wireless is generally more about multipath 'self' interference than brute signal strength. I don't know the 'logic' windows applies to latching on to a signal but it seems impenetrable to, erm, logic. Are there any big chunks of metal in the LOS (eg hot water tank or an upmarket range cooker) ?
While you can't beat a straight forward cable connection that isn't always possible. I did buy powerlink connectors (din't know about the sw interference) but a new router happened along (with 3 aerials) and that solved it, so haven't used the mains.
In teh early days I spent many (many many) hours faffing about with dlink stuff and wds with no consistent results (laptop would 'pick' the wrong signal) and only stopped when the wife decided I should do something more productive with my life.
So I think I would make sure neighbourly interference wasn't a problem (netstumbler or something), try channel extremes, make sure the network card settings are right and then if necessary spend £50 on something with lots of aerials !