Finishing basement. Need advice for receiver/speaker setup
The Denon receiver you linked to should do what you want -- it can output to 7 speakers plus a subwoofer, and it can play from a different source simultaneously through two of its speakers (the surround back R &amp; L). However, it's meant as a "home theater receiver" and not really a "multiroom audio receiver", so it may take some finicking with the settings to get everything to sound right. You might consider consulting a forum more suited for home audio enthusiasts for recommendations on specific receivers. At a minimum, I'd strongly suggest downloading the receiver's manual and reading through it to see if it has the options you need.

For your specific questions:


You need speaker wire. There are countless varieties of this, so just pick an option with a thick enough gauge (the longer the cable run, the thicker a gauge you'll want) and check that it's rated for in-wall use. Your speakers won't need any special type of connection (just strip the ends of each lead and plug the exposed copper into the jacks).
Ceiling speakers are, in my opinion, never going to give the best sound experience (there's a reason the standard home theater setup is to put speakers level with the listeners' ears). Assuming you're going to be putting out the same mono signal through each speaker, I don't think the particular layout of the speakers will make a huge difference. If you're interested in controlling each speaker's volume (or perhaps expanding your setup in the future), a multiroom receiver like this one I picked randomly might be a better choice.