Luxury! I dream of a house so big that two wifi networks still can't reach all of it! I don't know the technicalities, but is there some sort of relay device that would extend the range?
[rab] What a nice thing to say. [pen] Depends on the character of the problem. If I were in a big old house with thick old building materials I'd consider powerline adapter/access points, which would obviate the wiring problem and the signal-blocking walls problem and let you put wifi whereever you need it. It's also worth looking at whether the access points you have are up-to-date, as powerful/sensitive as they might be and reasonably sited to where you actually want them, and move/replace as appropriate. I just put in this model, originally intending to mount it in the ceiling central to the house -- there are generally fewer things to get in the way and absorb signal higher up -- but as it's a bungalow it's reaching everything quite well just sitting on a desk in the basement. What's nice about this one is that it projects signal in all directions including above and below, so it's ideal for placing in a ground floor ceiling of a two storey house. But again, I don't know what exactly what problem we're solving here.
I should have mentioned that yes, there are range extenders and they're probably fine, I just have no experience with them because they annoy the purist in me - one radio hop to the wired network ought to be enough for anyone. Plain repeaters are inexpensive and you can just stick one in, but effectively halve your wireless bandwidth. WDS by contrast is a relatively expensive technology which would require you to start from scratch and buy all the units from a single vendor. Again, I'd start by looking at the placement and performance of the ones you have.
And congratulations on moving in! When's the NetherPilg?