Megadeth tones are fairly easy on a recto, especially if you put el34's in it. Just crank the volume and not too much gain (vintage ch3 noon on the gain) and it gets right there, depending alot on the cab you use with it too.
i just sold my Rocktron Prophesy, which has Mustaine presets, which he says are exactly what he uses nowadays into a Line 6 solid state power amp.
honestly, as much as i like Megadeth, i thought the Prophesy Mustaine presets were terrible. very trebly and thin.
they might sound good to some, but not me.