I would suggest to have a look at http://xpenology.com/forum/viewtopic.php?f=2&t=10973 to see if all the hardware you will buy is supported.
If you are planning to go virtual (ESXi maybe?), my advise would be to go for a platform wich supports VMDirectPath, so you can use a cheap controler. https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=2142307
Baremetal is the simpelest way to get up and running. Just write an USB stick and you're away. (and maybe, depending on your hardware tweak the lancard)
I just bought a Proliant ML10v2 runs really nice and not to expensive....