If your Marantz 7007 receiver
can setup without a center channel speaker, you can
get two matching "center channel" speakers instead of three, use it as left and right front speaker as @auxinput suggested.
https://www.crutchfield.com/p_107SIGS30/Polk-Audio-Signature-S30-Washed-Black-Walnut.html?awcp=&...
https://www.crutchfield.com/p_107SIGS30/Polk-Audio-Signature-S30-Washed-Black-Walnut.html?awcp=&...