Yes, the preference is there, I have it as well.
Try the following: Uninstall a game (say, Sins or GC2). Install via Impulse. Choose the path. Impulse adds /Stardock/Totalgaming.net/ after your selection.
At least as of two weeks ago, when I installed Sword of the Stars. Chose F:\SotS, got F:\SotS\Stardock\Totalgamin.net - had to copy it manually and update all registry entries as well. I first reported this issue about the time Twilight came out, again in May, in June for SotS... So far no response on the Impulse board, which I find slightly frustrating.
The latest SotS update (1.5.2) wasn't on Impulse, yet SDC showed it perfectly.