[cd34]

Relative Speeds:

P3/800 = 1
P4/2.4 Celeron = 3x faster than p3/800
P4/3.0 with Hyperthreading = 5.5x faster than P3/800
P4 Dual Core 3.0ghz = 7.5x faster
core2duo 2.4ghz = 11x faster

Now, you can really vary those numbers considerably by using dual channel ram, the fastest speed ram you can put in the machine, etc. Don't overlook hard drive performance either. A 7200 rpm drive is going to be faster than 5400. 10k and 15k drives are not uncommon these days and a decent sized cache on the hard drive is also a boost.

This isn't to say that a P3/800 serving static pages can't easily fill a 100mb/sec pipe and still serve responsively, it just depends on how much calculation you are doing to actually serve the page. The more static/less dynamic the page the less CPU horsepower you need. If you start getting into traffic trading scripts, dynamically generated pages, etc, then, you of course will need more cpu horsepower.

The tradeoff you need to decide is -- if you have enough cpu now, then maybe take a smaller step up on cpu and spend the extra money on more bandwidth. However, if you intend to get into more dynamic sites, perhaps decide for more cpu & more bandwidth.