Lab workstation alternatives to Dell T500 but similar spec / chipset configuration?

I'm looking to supplement my existing Dell T5500. The plan was to just get another T5500, a Xeon X5650, and 24GB registered ECC RAM to make it identical to my existing box, but I'm having a hard time finding a good price on eBay for the second box.

Anyone know a good alternative that will work in conjunction with my T5500 with ESXI 6.5 and that I can utilize advanced ESXI/vCenter functionality with? Things like EVC, vMotion, fault tolerance, and HA?

I was looking at the HP z600, but I'm on the fence because there are early revisions of it that don't support registered memory.