On getting a Bugera schematic Bugera is Behringer and they do not send out schematics. The Bugera does have solid state reverb I traced out the amp and posted a schematic over at Sewatt once upon a time (bug era). The speaker in the Bugera and the Crate are both not great the Crate is real bad the Bugera is dark. For a 10 inch you can consider an Eminance Legend 10516 which is 16 ohms that is what the output transformer in the Crate is really wound for or look at Weber speakers. For Crate schematics Crate will e mail a PDF to you no problem. As far as tone, op amps in the front end lead to a cold sound to me so I would get rid of it. The op amp is used as the volume control in the amplifier and to give a treble boost to work with the tone control located between the two triodes in the preamp section. If you remove the op amp to regain the brightness for the tone control you can use a 470nf cap for the cathode bypass of the input stage triode. There is a thread on the Crate over at Sewatt and Sewatt is a good site to go to relative to amp building and mods.