I don't think you'll have any problems with them sitting that close, other than concerns over the potential bass output.
In my HT, I had LS9's in the front, approximately 9 feet from the first row of seats and 16 feet from the second row. Sides were LS9s and were 8 feet from the sides of the end chairs. The rears were LS6's and were about 7 feet from the second row.
Never had a problem, other than being cramped for space.
I think you'll be just fine.