Don't get me wrong, I love grill marks as much as the next guy, but in reality, they don't mean anything. You want that nice crust that forms by searing the meat close to high heat. The grill marks may not show as well because the crust is nice and thick, but the flavor will be awesome.
2013 Stumps Classic - Delivered 4/15/13
Large BGE - Rescued 2012
2010 WSM 22.5"
2010 Weber genesis gas grill
Rescued 22.5 Weber One-touch gold
BBQ Guru CyberQ
2011 Built UDS - Retired