Unless you're planning on doing some mods to the JCM800, I'd probably stay with one of the 5150's or the Blue Voodoo. The JCM800 can get some great tones, but I don't consider it that great for death... and you'd probably want to try it with some kind of boost to the input stage, with an EMG PA2 or a distortion pedal set to boost.
Hope you get something in your range that you're happy with though.