I have an HP Proliant ML350, that was no longer being used by my work, that I was able to transform over to WHS 2011. The only real trouble I had was the drivers for the existing system. Fortunately, they were all saved in a pre stored ROM. All I had to do was point to that when installing WHS, and it was seamless from there.
I don't have it fully utilized yet. It has an SAS controller, (that I've installed SATA drives to...) and a RAID card. (I am unfamiliar with RAID, and have been doing as much reading as I can) I need to buy more drives and implement backups, as well as backup my existing server to it.
"Once you learn good English...Can't nobody take it away!"
Xbox LIVE Gamertag: KEVIN G 40