It doesn't necessarily have to be the Powerline adapters - if the wiring in your house is old and/or not of the best quality, that might affect performance as well. Same if there are different circuits involved.
If modprobe returns nothing, it means everything went fine. If you're anxious for feedback you can always use the -v option . Try setting your network up the basic way (ie wireless_tools + wpa_supplicant) to see if that works, then try the GUI thingy.