A minimal system is control10 and twinstore, is that correct?
You need at least one of each of the following:
1) Sooloos core - Control:10, Source One, Ensemble
2) Storage - Ensemble, TwinStore
3) Controller - Control:10, PC/Mac application, iPhone/iTouch, iPad, Crestron (via the source bridge).
Obviously, a single Ensemble takes care of (1) and (2) and a Control:10 would take care of (1) and (3).
Optionally, you can add additional zones with additional Control 10s, Source Ones and, of course, ID40 cards.