Does anyone know the estimated number of sites that can be hosted on a single RaQ 4i?

Sites would be HTML/PHP only, no mySQL, no CGI and no SSI.

Cobalt RaQ4i's have a hard limit of 250 sites, but that can be changed. Its really hard to say how many site can be hosted, but on average I would say 100-200 and maybe 350 max. Again, it all depends on the load each site places on the server, so its impossible to say for sure.

I would say nothing over 125 sites......on the safe side.
512 SDRAM is the basics.

When cobalt states up to 250 sites, but hey, you've got to leave room for extra administration tasks, multiple crons etc, or you will see yourself rebooting the server more often.

But it still depends on the sites that you host.

We cap it at 100 at our company for each raq.

We cap it at 100 at our company for each raq.
I would have to aggree w/ ya. The cobalt servers, I dont think, are very good and 100 customers on the server is about right. If you put too many on these servers you start to run in to trouble. Thats from personal experiance.

We only have two RaQs. We host about 155 sites on one and close to 200 sites on the other. These are all of course very small accounts and are all static. MySQL is not even installed on these servers and DNS is not even running on these machines either.

Also, I have never seen the load average exceed 1.00 (if that)

This will only depend on the type of sites that you run there. You won't even be able to know until you start putting accounts in. :)