I've also got a Valveking 112. Awesome little amp! The stock power tubes are crap! I put a set of Ruby 6L6's in mine, simply because I had some extras laying around, and it made a noticable difference. It was noticably louder, and had more definition to the tone. I would also highly suggest JJ 6L6's. Those are some great sounding power tubes as well.

Not sure what to tell you about the hum. I would start with your cables. A bad cable can make that "blowing into a mic" sound. Does the amp make the noise without anything plugged into the input? I'm not sure what to tell you if that isn't it. If it's not your cables, I would suspect the preamp tubes to be the culprit of that noise, but I could definitely be wrong on that. Power amp tubes usually wear out long before preamp tubes do. When they do, it will normally cause a loss in volume, sudden volume drops, blown fuses, etc... Do a forum search on the topic. There have been numerous threads about tube amps making funny noises.