Nope, any expansion will do. My partner and I share our sims 3 games, so for a while only one of us could have an account. Then we got some expansion packs, and I was able to use those to create an account. I've uploaded a couple of things to the exchange without any problems. I can't download directly from the exchange - it always says I need a store update, even though I'm pretty sure I do - but I don't know if that's related to the fact that I don't have the base game registered. I can, however, download indirectly, and I've bought + downloaded from the store without any problems. Either way, give it a try - I think it'll be fine.