you seem like cash isnt an issue with buying new antennas and repeaters. ethernet over power would be my second option. my first option would be running ethernet cable out windows between your hub and devices, or through the ceiling/ vents/ attic. it maybe cheaper to hire an electrician to run cat5e or cat6 cable through your home. why on earth do you have 6 walls to go through?
Cash is definitely an issue. The g router is 6 years old, so I've had it and the repeater was actually given to me. So far, I've managed to spend under $90 to get everything accomplished, which was the cost of the new router. The electrician would cost more than that for certain, at least here.
As for 6 walls, that's just how it is. The rooms in between aren't mine to make that decision, so that's a definite no.