I would strongly advocate against using Plone ( 1 year of experience ). Slow, inflexible, data goes into a database which nobody uses and is not a database by any stretch of imagination. Effectively you are now locked in.

Even for a moderate site you would need a caching proxy in front. Code is not pythonic at all, but a java-esq class hierarchy over 15 levels deep.

Very small user base, little online help.

Will never touch again.