The Raq 550's are/were great servers, in my opinion. It is too bad that they are now going EOL. I thought that the GUI and built-in features on the 550 were by far the best to date for that entire line of server appliances.
One alternative source of well-built servers that you may want to check out is http://www.cavaliericomputing.com
. The owner, Bill Cavalieri, is a great guy and we've bought a bunch of servers from him and we're very happy with it.
Plus his pricing for rackmount servers is among the best that I've seen anywhere. I've also heard good things about SuperMicro although I have never bought one of their servers so I can't speak from first hand experience on that.