Need a VPS, requirements?

I think I have outgrown shared hosting at Dreamhost, who I might add have been pretty good over the years.

This is what I currently host at Dreamhost and possibly someone can tell me approx. what I would need in a VPS.

Domains Hosted:
21 plus 2 subdomains

Email addresses:
50+

MySQL Databases:
11

Applications in use:
WordPress
Online Invoicing System 3.0
PHPlist (Never more than 800 emails per month/sending)
Machform (Contact form)

I don’t tend to use massive amounts…