Master 250 Ex pro + (old) 250 companion make a 1000?

[ogs]

You might get it to work, but the companion config from a Pro CI pair will probably not work with a non-pro. Try the companion config created for an old 250 pair. If you're lucky that may work. The two amplifiers sound different, you'll probably notice. If there is a level difference the balance control should take care of that. Good luck!