Rockerverb 50 Combo tube replacement/upgrade? Suggestions?

[jessedavid]

I have had a Rockerverb 50 combo amp for almost 4 years now and have not replaced any of the tubes nor had any servicing done to the amp during this time. I don't play this amp as frequently as I used to but when I do I am pushing it pretty hard and using a THD HotPlate to kick back the volume. Recently I have noticed a LOT more hum coming from the distortion channel and the loop channel seems to be picking up my delays tap tempo (hearing a subtle tap). I am assuming that it is now time to get the amp serviced and the tubes replaced and biased. I love the tone of this amp and the response but I wanted to see if anyone had any suggestions for tube replacements, specifically for the style of heavier rock to progressive metal. I am looking into purchasing an ENGL Powerball but in the meantime I was wondering if there were any tube modifications that I could make to make my Orange a bit more aggressive without loosing the tonal quality of Orange. All suggestions are greatly appreciated!