It depends a lot on what kind of sound you're looking for. Best bet is to try out several tube amps.

I just went through this and for my taste, the Fender Blues Junior gets non-linear too easily - if I played the strings softly it was OK, but if I plucked with any enthusiasm, it quickly became distorted.

I also bought an returned a Superchamp XD. It looked great on paper, but on both the clean channel and the supposedly clean voice #16 on channel 2 there is a terrible amount of hissing noise if you have the reverb turned up. This doesn't happen with tremolo or chorus - just reverb. I thought my amp was defective, so I checked several others in music stores and found that all of the SCXD's hiss. I was using humbuckers and a Mogami cable, so it's definately a problem in the digitial effects section of the amp. Too bad, because it was great otherwise.

I ended up buying a used 65 twin reverb reissue which is much larger than I wanted, but it stay nice and clean.