Been playing around today and issued the top command in a terminal on the host machine to see and it's showing the same thing. The overall CPU usage of the machine is low, as in 5% of less, however it's showing very high CPU of each virtual machine. Here's a screenshot to show what I'm talking about. You'll see load averages and overall CPU usage shows low, ever each individual Virtualbox instance show's high.

Problem I've been having is the CPU of both my virtual machines are showing very high in Gnome monitor. However, load averages are low, and also as you can see from the screen shot, the overall CPU of the host machine show's low. I have yet to figure out if the two virtual machines truly are using a whack load of CPU, or if not. Now within both virtual machines, they both show very low CPU as well. Although I know virtualbox isn't the best virtualization software, I found it the easiest to install and play around with. Especially for just a little home server. I may be moving to VMware Server soon, as ESXi doesn't like my raid controller.
Server specs are as follows:
Athlon X2 6000+
8GB DDR3
2 x 750GB in raid
10Mb download, 2Mb upload bonded mlppp ADSL2 lines for this box alone