When I was testing titled vs flat with 'T' brackets, I could tell no difference directionly. I recommend flat against the wall for a cleaner look and keep the $100 in your pocket. But be sure you have some space above QS8. Alan says 2-3 inches is OK. My gut thinks 6"or a bit more might be better than OK. ;o)
my 2¢ (may be worth less in this economy)

Dave

"In theory, practice and theory are the same. In practice they're not."