Second Row & Front speakers

[derelicte]

I've got some space (and a spare couch) and was thinking of adding a second row to my HT. I've got it set up and even without a riser you can see the screen just fine. Eventually I'll include a riser, but I got to thinking about sound...

Should the second row have line-of-sight to the front speakers to ensure decent sound quality?
It's not a big deal right now, but I'm in the process of building a bigger screen (fixed) and it would likely entail moving the bottom of the screen down a bit (and the center channel with it). This should be okay for the front row - but what about those behind?

Thoughts & suggestions appreciated!