Your AVR should be able to drive these 6 Ohm speakers well, but at 75 watts/channel don't expect near reference levels. For wiring gauge vs length, check the following table: http://www.roger-russell.com/wire/wire.htm#wiretable As you can see, 14 AWG should be just fine. I cannot get information on the bookshelf speakers from the Aperion website, so you might want to contact them about the details when using wall mount brackets.