73bruin - The manual is available online as a .pdf in the 990 product page. I find it very useful when I need to use it. I keep it on my desktop so it is easy to access when needed.

With regards to the wiring for a 7th speaker, I bought some 4 strand phone cable which I used to power my rear surrounds awhile back before I buried the wire under some new carpet. If you can only run one wire to your rears it would serve to power both speakers and is pretty cheap. I think it is 24 gauge but it is solid copper. It powers the rears pretty well.