I would start by reading through microsoft white papers on scailablility. There are several factors above and beyond what you have listed. Number of people connecting to it, concurrent connections, and amount of data per client just to name a few. A database with 10gb of data and 10,000 clients needs something drasticly diffrent than a 1TB database with 2 clients attached. No one here can give you a blanket recommendation.

Wes