Newer routers can run mixed 802.11 b/g/n which is probably the best current domestic solution going, that would likely improve your situation if you have wireless clients that support it. Switching to an 802.11n router would be good for you if your neighbours follow suite. 5Ghz has a harder time penetrating walls et al (shorter distance, higher speed)
Power over Ethernet adapters work pretty well. You should be able to easily find some with good reviews on line for not that much money. Unless your house has really old crappy wiring you can get good speed too (50Mbps for example is plenty for most home networks if you are used to wireless speeds, higher speeds often require pricier more lavish units).
Sadly I have no advice regarding how to tame your Linux wifi client adapters though, only the alternative solutions.
Cheers, James.