Planning for Website traffic on a self-hosted web server

[GLogic]

How would you plan for the levels of traffic on an in-house web server?

The scenario is that website is basically running on a T1 (1.5 Mbps) connection pipe, and traffic projects to increase significantly with content growing from about 40 uniques a day (on less than 20 poorly optimized web pages + associated PDF documents), to over 150 search optimized content pages + offsite traffic and link building.

I'm trying to figure out what kinds of avg traffic levels (plus spikes) would represent a maximum bandwidth capacity for this...given that its a narrow specialty B2B focus.

Any answers would be useful.