A lot of the CEH 'hands on' stuff requires at least a Linux box and a 2K server. The Linux machine can theoretically run any distro, but you'd be daft to run anything other than BackTrack as it has everything you would possibly need already preinstalled. The 2K server should be unpatched - you're using it as a 'Proof Of Concept' machine, not as something you would encounter very often in the real world.
So, instead of investing in a super duper box to run loads of VMWare machines on, you would probably be better off investing in another box to install 2K server on and a switch so that you can do things like ARP spoofing on. BackTrack is a bootable distro so you can boot from it on your current workstation.
The problem with VMWare for this type of thing is that it's very hard to get everything set up and working properly when you are sodding around with packet crafting and what not - because you are basically using the same underlying TCP/IP stack. Lots of the labs I've been doing this week (I'm taking a CEH class right now!) haven't worked properly on VMs because of this.
Of course, a nice big machine to run VMs on will certainly stand you in good stead for future certs, so it's probably a sound investment anyway.