Workstation or exGaming Rig?

[pred8tr]

I need a Virtualization box to run the following guests:

Windows Home Server 2011 (24x7 backing up all my desktops and network dvr)
AsteriskNow (24x7 servicing one 7941G and my mobile phone)
CentOS RHCE lab machine 1 (as needed)
CentOS RHCE lab machine 2 (as needed)
CentOS RHCE lab machine 3 (as needed)
Windows 7 (As needed, maybe persistent)
Fedora, Ubuntu, or whatever flavor of linux I feel like (As needed, maybe persistent)

I was going to run esxi (I originally picked up a Dimension 9200, 4x1GB DDR2, for this but it has no VTX and Q6600's (best cpu it can run) are $100) but now I am leaning toward RedHat KVM since I will have to learn it anyway.

I planned to recycle my old gaming rig hardware to suit this need.

Phenom II x2 555BE
2x2GB DDR3

I would need to buy a motherboard and a case and more ram. I have PSU's and everything else lying around.

Then I started looking at old Workstations like the HP xw8400 and xw8600.

I sourced an xw8400 with dual Xeon 5060 (3.2HT) cpu's and 10GB of RAM for $200.
Unfortunately, these are P4 class Xeons so I worry it wouldn't fit the bill.

The I sourced an xw8600 HP with (1) Xeon X5260 Dual-Core 3.33GHz (I can add another of the exact cpu later if needed), 4GB, 250GB HD, gfx, and all. The entire system for $239. For $45 I'd pick up another 8GB of FB-DIMM ram.

But all this leads me to the following question.

Is there really any benefit to using OLDER workstation class hardware as compared to using my old gaming rig stuff and building this box like I do most of my rigs?

Granted. I can do a LOT on a gaming rig with $300... but I feel like a dual processor Xeon box may have some advantages.