Upgrade path...Need suggestions

Current system for 2 channel:
Arcam Alpha SE8 cd to
B&K Ref 20 to
Bryston 3bst to
Gallo 3.1's 88db sensitivity
System is also used for h/t
My first thought was to upgrade the B&K to a tubed pre but after some looking I found no tubed pre's in my price range that had zone 2 which is very important to us.
Now I am thinking about an amp upgrade. Have never had tubes but want to give it a try. How much fiddling do they require? Keep reading about biasing, pentode, triode etc. and have no idea what it means. Is it a constant battle or set it and forget it? How much tube power do I need?
Budget is <$1000 so used is the way I want to go. Would like to get some recommendations. Looking for that "tube" sound. Soundstage, warmth, detail, midrange, etc..
Thanks for any suggestions.
Steve