These pix are taken while there was 53 members reported online concurrently. Look at the server load, is it because of XOOPS or not? ouch... my server crashes every three hours if I don't restart httpd
Notice that admin1 is the only domain with xoops

That's not right.

What are the "php" processes? CGI? I've only run PHP as a compiled in module (Apache 1.3x) and a loadable module (Apache 2.x) and have never seen php as a process or loads anywhere near what you are seeing.

Perhaps a phpinfo() output would be useful for diagnosis.
<?php
phpinfo();
?>

FYI:

That was the CGI version of PHP eating up the CPU. Running as a module PHP is better behaved for CPU load. You don't always have the option to change it but for performance it is better as a module.

One caveat to anyone changing from CGI to Module is that the Physical_Path may change in some server setups so you might have to change 'XOOPS_ROOT_PATH' in your mainfile.php.

Also, for an XOOPS server it is much better using a PIII/IV over a Celeron. A Celery can work very hard trying to keep up with the queries.