The "CPU juice" required of a server, per page sent, is fairly low compared to the "juice" a client uses to run the browser that page is rendered in. Run munin,

The "CPU juice" required of a server, per page sent, is fairly low compared to the "juice" a client uses to run the browser that page is rendered in. Run munin, awstats, and top to get a feel for your server load: you should get a sense of how much it takes to manage one user, and how many simultaneous users you have, etc. For development, assuming you have another machine for your GUI, a 400 MHz Apple G3 B&W with 256 MB RAM will run Debian Lenny with Apache and PHP just fine (http://en.wikipedia.org/wiki/Power_Macintosh_G3_%28Blue_%26_White%29 http://en.wikipedia.org/wiki/Power_Macintosh_G3_%28Blue_%26_...), so I would think any of the plugs would be fine. If you are deploying a service and marketing it to millions, you're going to need a bit more than a plug :-)