I've tried all sorts of brands but in the end came back to Apple stuff.
As far as being able to reach more of the house, I believe current best practice is to place multiple access points. So simply claim a new extreme under the warranty, and get an additional Airport Express for the top floor (or the other side of the house).
To link them together, put Ethernet cable in place, or if that's absolutely not possible, get a Homeplug set of adapters.