For your set-up make sure you use speaker cable rated for in-wall use. This will be necessary to pass the building code in most locations. Your other option is to run the speaker wire in conduit.

I also disagree that 16 gauge wire is all that is necessary for your application. I would suggest at least 14 gauge wire since some of your runs will be in excess of 20 feet when you include all the bends plus you want to leave some slack.

Lastly, I do agree that designer brands are not necessary. You should check out some other vendors such as Parts Express or Audio Advisor . Audio advisor does tend to be a little pricey but you can get some good deals in their clearance section. I picked up some in-wall rated 14/4 speaker cable from them for a really good price.

I use Leviton Quick-Port Wall Plates. They are very flexible in their design. You can buy the plates and various connectors at Home Depot or online at numerous vendors.