I've heard the suggestion that you put the side surrounds one third of the distance between the first and second row back from the first row. This is to help out with the side surround effects in the back row, though they are still coming from slightly in front of you, but not hurt the side surround effects in the first row. Going with rear surrounds on the back wall will also help to anchor the surround effects a bit more so that they don't feel like they are all coming from in front of you. I don't have a two row setup (but hope to in the near future), but I'm just letting you know what I've read and heard and putting it together with some common sense.
Three rows, who knows what works best. Probably two sets of side surrounds.
