Guys, today I made an impulse buy: new old stock Marshall JCM 900 model 4100 Dual Reverb re-issue from 2008. It is the 100W version with 4x 5881 power tubes. Sound good even with Master Volume on 1. Can't wait to crank it up real good! The price was EUR 767 or $902, with 24 months warranty from the store I bought it. Can you tell me is it possible to replace the 5881 tubes with EL34s or something else? Is it worth it? Any tips/tricks with this beast are welcome!