I would like to see 350£ esxi test bed bundle
.
And please don't send me a link to hp microserver as I've tried few hypervisors on it and it's not fast enough.
Also you mention about ram but you never mention about hard drives which are main bootlenecks if we talk about virtualization. You can run linux server without gui and it will happily run utilizing 256 ram but try to run 10 instances at the same time and simulate some load... single harddrive will never cope with it.
Regarding the power supply:
http://www.ebuyer.com/442064-coolerm...k350-kwp500-n2
Finaly about the mobo and controller...
tbh with you look at the budget, also bare in mind that he wants it for windows server experiance.
I've been running both ESXi and Citrix Xen Server on similar build with pehenom 2x4 and asrock mobo and guess what, it worked fine, surly it wouldn't be sufficient for business use but it is more than enough for learning/file server.