I have computers scattered across our home, and in many areas it is not feasible to run ethernet cable. At one location (less than 30 feet away) but through multiple walls, I can barely connect to any POS (I have two). I added a stand alone antenna extension with long antennas on both the router and the WiFi card on the PC, however, this made zero improvement.
What should I be looking to purchase to increase the signal strength? I've already tried different routers. Thanks if you have any good ideas.
There is very little that can be done to boost the power on a consumer wireless router. If the router is at one end of the home, there are antenna add-ons that can be created that will increase the signal strength in one direction. Freeantennas.com has templates that will boost the gain of the output of your router. http://freeantennas.com/projects/template2/index.html This one actually works pretty good.
No, any repeater can be used as long as it's compatible with your network (such as g or n)
But I would check out Whj2u99's suggestion first. If you already have 2 APs it's unlikely they're centrally located and you could deflect the signal from one or both of them into the areas where your signal strength isn't as good. It sounds odd but it's a good no cost solution to extend wireless ranges just a little bit further.