Hi. As I am doing one right now just like you, I just want to share some info I got.

Go HERE for some great advice about getting dipolar or bipolar speakers, and the speaker's placement especially for the surrounds.

For me I will be using a 2nd hand Bipolar as left and right surround, and a direct firing as rear surrounds.

Placement of surrounds are ideally about 3 feet above audience head level. But do check the article above for the positioning of either Bi or Dipolar speakers. (If you don't know what they are, the above excellent article do explain it well.)

Hope that helps.

About the concealing cable, I got them from Monoprice and ebay. One is obviously Monoprice item, with I think 12AWG certified for inwall concealing, another one is Monster cable of 35ft each, priced quite ok even with transport all the way to Malaysia.

If I were to do it all over again, I will order 200ft 12AWG in-wall rated cable from Monoprice in one go instead. Plus other misc hdmi cables, RCA cables.. etc etc.. in one shipping !