I found Baldwin 12AU7's to be the best one of that type.
The 6922 or 6DJ8's could be almost anything you want, depending on the type of sound you need - sharp, smooth, dynamic, mellow, bloomy. Each brand of 6922 has it's own character and this unit will show you all of that. It is the tone control in this unit, IMO.
I also owned a Debut II amp for a while, and while it was very nice it didn't drive my speakers very well. I sold it to a friend and it sang in his system. More efficient speakers than mine. Truly a great amp.