Actually, it should work. Remember, I go back to tube days, when they were new. They SHOULD work but I've been conditioned to not do so. In such case, your adapter and any amp will work but it would be a waste of a good stereo. Your final solution would probable be cheaper in the long run..
For my 6.1 Denon, I tell it there is no 6th speaker. Yeah, 6.1. I bought at just the right time, didn't I?