Need to have about 10 DBs working on one server.
3 of them (10GB, 3GB, and 3GB .MDF files) are intensively used, while other 7 (kind of same sizes) are used on need, usually for some reports creation.
I have a server (HP DL360G7, 24GB memory) with 8 SAS:
2 * 300GB, 10k
6 * 146GB, 15K