In many of the SM related books I have read recently they refer to the SM as "towering", "giant", "enormous" and so on. But I have also seen where they use "two meters" multiple times to denote this grand stature... Now I may just be a "daft yank" but..um.. isn't that just 6 feet or so?
Now 3-4 Meters is huge but 2 is shorter than most of the players in the NBA and I am pretty sure the fluff and intent is that they would be at least that tall if not taller. I mean when I envision an Astartes I picture someone like Broc Lesner from the UFC/WWE sport but magnified a good 2-3 feet in every direction.
A 6 foot tall dude just doesn't sound all thet intimidating to me, but then again maybe all the brits are really short?