Hi, I'm planning building a VMWare Virtual Lab and I'm considering buying a used T5500. Questions regarding this build will this be good enough to run VMWare ESXi 5.1, and if something goes bad with my PSU can I replace it with Seasonic Platinum series for example? I will be running Windows 2012 Server, exchange, Winodws 7, 8 to test and learn...
You should be able to replace the power supply with a third-party PSU.
The configuration should be ok - you probably won't be able to run Exchange in a VM with much else with this configuration). Your real bottleneck is going to be the controller. I would recommend using a PERC 6/i not a SAS 6/iR. It seems to come with a single 300GB SAS disk ... are you getting more disks?