The Qs8's are very forgiving, meaning that you can place them about anywhere and get great results, you just don't want them right above your head. If you can space them out a little, either behind or to the sides or side/back corners they will work. Are you planning on pre-running the wires in the walls/ceiling?

The Yamaha's will be just fine and sound great, the only problem a few have had is when matched with the M80ti's which are 4 ohm speakers.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85