need some help help trying to setup HT.

I have KEF cresta 10 and soundstage 1.5 tubamp with sony NS76H.

future add HTPC, so right now need to add mid and subwoofer. I also want to enjoy sterero so intend to buy Marantz cd player .

so can I know if I buy Onkyo say 6 series, can I just forgt the soundstage 1.5 ??