httpd processes, memory and high server load

It could just be a simple configuration issue leaving you unoptimized
for the amount of traffic and accounts that you have on your server.

Other than the above though ...

At the levels you are talking about, I would consider going to 4GB to
return back to physical memory from swap partition or possibly getting
an additional server to split and lighten the traffic loads if you can't
isolate the issue within the configuration.

However, I also would want to know what is causing the traffic and
would first take a close look at the site statistics and log files and
find out if you have any particular account that is using up an
excessive amount of simultaneous traffic as that is often a sign that
someone is doing something they shouldn't be doing.

Some areas of interest ...

Code:

/var/log   (see 'messages' and 'secure' in particular)

/usr/local/apache/logs 

/usr/local/apache/domlogs   (Try an 'ls -lSr | tail -5')

/usr/local/cpanel/logs

Should also check running processes closer ('ps -ef | less')

If the above doesn't help you nail down the issue, I would be glad to take
a look around if you want a better assessment as to what is actually
going on with your server and it's traffic and could let you know if you
have any potential security issues that should be addressed in the process.