Roger, As far as i know, if you dont have pre-outs for the powered amp, then you will not be able to do this. You may want to look into getting the next model level for the HK and that one i am sure has the pre-puts.
I have a HK 445 and Toshiba A2, and thinking about gettinga blue ray player, right now I have the HDMI going to the TV and optical going to Receiver, this is ok?