Maybe my opinion is different, but I think all of the Soldano amps are equally as good. There is something special about the SLO that no other amp has. However, none of the other Soldanos lack anything. The Avenger sounds really great, and it's plenty of amp if you don't have much use for a clean channel. The Hot Rod CAN do some nice cleanish tones, but really excels in the in-between sounds and gain.
The two most underrated and underappreciated amps in the Soldano line are the Decatone and Lucky 13. A lot of people rag on the Decatone, but they almost always judge it on channel 3. To me, channel 1 & 2 are where the Decatone shine the most. I also love channel 3 and have no complaints about the Decatone overall except maybe the same thing everyone complains about Soldanos is the FX loop - but it's not a bad FX loop either.
The Lucky 13 flies under the radar too often, but it has a LOT to offer. It has a unique sound, and the clean channel is heavenly. What a lot of people don't know is that you can call Mike Soldano and order a 25w Lucky 13 if you want, and knowing him, he won't charge you extra either. Mike is a great guy, very reasonable, and willing to go out of his way to satisfy customers. I've spoken to him a few times over the phone and he never sounded rushed. He always takes the time to explain things and answer questions. The dude is a living legend.
Anyway, if you can find a good deal on an Avenger, get one. It's a great amp to have around and you can find lots of great clips on youtube. The 50w or 100w, doesn't matter. Both sound awesome and can do low volume pretty well too.