An important point though is that one of these days, (literally), the community update to GC2 will be released after some Stardock polish is added, and I am thinking anybody who plays GC2, which are a few lol, will want that update. It makes the research trees for TotA better among other things. And I am thinking it will be easiest to get it off Steam, though truth be told you can get the current version now (including an update to the executable provided by SD) which is working quite well (have to say that, I helped about 0.01%) from the GC2 forums.
I have a number of games that I bought from Steam so I don't have to get up and put in a disk. Just put 'em on the wishlist and let it cook.