FLV files: progressive vs streaming

We have several clients who will want to display video on their sites.
The most common file size of the flv videos will be targeted at 1.5 to 2.5 megs.
And the length for each will be targeted at between 30- and 60 seconds.

What delivery type is recommended, progressive or streaming and what should the server specs be?
We expect to about 10k -20k total page views per day on a dedicated server with a 100mbit uplink.