I notice it's an AMD system rather than Intel. Probably not a problem, but just double check.
My whole home server system is based on VMWare ESXi 5.x. Made a few limiting mistakes, but it still has been great.
I bought a Fujitsu server on NewEgg for $299 along with 4 2TB drives. I then bought a Dell Perc 5 Scsi card on eBay for RAID storage. I run the VMWare off of a USB key rather than the HD. I recommend this so that you can devote all of your hard drive storage to VMs and nothing to the ESX OS.
I'm running WHS 2011 as my main server VM and a Win 7 VM for utility purposes.
Problems: Turns out the SCSI card really isn't supported by Fujitsu. Their own SCSI card costs more than the PC - so forget that. But I haven't been able to run more than 8GB of RAM on the machine. So these two VMs are really all I can do at the moment.
Also, any kind of USB connectivity is flaky. And ESXi doesn't offer much in talking with a UPS. So power outages always freak me out.
If you're just going to do one HD, then you don't need to worry about SCSI. But if you want multiple drives, then SCSI matters. You might want to look at the HP line of Micro Servers in comparison.
Welcome to the world of home servers!