I would be interested in what other Ultra owners are using for tubes. I ordered mine without tubes, and for the 8 preamp tubes, I chose Nationals from Upscale Audio. Thy have been great. But recently, I heard something that made me get the heavy duty wallet crowbar out: these Siemens tubes. I tend to be a bit of a detail freak, and for me, that goes hand in glove with soundstage and depth. These tubes knocked my socks off in those departments when I listened to the Cantate Domino, and I fully expect the Ultra to take great advantage of them.