Two receivers, one Abus, one question!!

I have an onkyo pushing 7.1 in basement livingroom with pre-outs to a cheap Sherwood receiver that runs (via speaker selector) 4 bar speakers, 2 poker room speakers, outdoor speakers, and office speakers (4zone) and it sounds great.

I have an Abus system on the mail level of home and have ran RCA's (and cat5 and cat6 just to be sure) to the Abus before I finished the basement.

My question is how to integrate the system in basement w Abus? I thought pre-outs but the other receiver doesn't have them and I don't think I can split preouts from onkyo (one to Abus and one to Sherwood).

Can I integrate the Abus without replacing the Sherwood with a new receiver has preouts?

Thx everyone...

Abus by russound. Self contained whole house audio. Builders have homes here pre-wired for it since it costs nothing (some cat5).

So splitting the pre outs on the onkyo has no effect on the onkyo or sound quality to other amp?