Looking to build (or buy) an ESXi host for lab environment

I do work within the IT industry, and have a very poor lab (running VM's on my gaming machine and a Pentium D machine someone was getting rid of). I'm looking to build a lab that I can spin up machines. This would ideally be a machine I plug into my router, I can spin up machines and rdp/ssh to them from my desktop. At the same time, I have a rather old Snort machine that is sucking up the power (core 2, ide harddrives). I would like to retire this to save space and electricity. This will require an additional 2 fast ethernet (gigabit?) ports on this ESXi host. I am okay with spending a little more for lower power parts.

What I need device to have:

-Run a mixture of machines of various OS at a time (Windows, Windows Server, Linux..) 

-Looking to have ~5 machines up and running at any 1 time

-16gb of ram (or more)

-4-8 cores

-2.0ghz (or more)

-4 ethernet/gigabit ports

 

What I need it to be physically

- not concerned about case/form factor

Power

-would like low power usage from parts 

-Intel Atoms are currently what I am looking at (and go up to 8 cores very inexpensively)

-SSD's have very low power 

 

Budget

- $1000-1300 (Canadian)

 

My current idea for this build is a supermicro machine which comes with power supply, mobo, chassis and proc: http://www.ncix.com/detail/supermicro-5018a-tn4-1u-atom-c2750-03-95608.htm
I just need 16GB ECC memory (~$200), a SSD (~$100), and a WD Blue 1TB ($65).
This works out to about $1100.

Is there a tower build I can get (or build) that would be better on power? or Cheaper?