mamaliga

Planning to open a tube next month but before this would like to know what server configuration fit my needs.
It will be a medium size tube site with not more than 300 simultaneously members online and for the first month plan to add around 1000 videos average between 100-600 MB each.
Will be enough only one strong server for me or should i start at the begining with 2 not-so-strong servers ? And why? Please explain.
Thinking about to use nginx and varnish cache
Please no spam offers (yet).