Welcome to AH,
First, the Marantz SR8012 can drive most speakers except the ones which have weird impedance values at low frequencies or critical phase angle response, when playing at very high sound pressure levels..
Do you have access to stores where you can listen to a variety of speakers? If so, this is what I suggest you do as a first step. As a matter of fact, you are going to live with the speakers you purchased. It would be the ideal situation if you could have the speakers you like driven by the Marantz AVR which you are considering. Also, if you could take the speakers home to hear what they sound like in your listening room before making the final decision, that would be the best solution.
As to the need for a subwoofer, that depends on the speakers that you are going to choose as the front left, center and right speakers, and the type of music played or other source content. Will they be bookshelves or towers and what will be the size of the woofers? Do you intend to watch action movies with a lot of bass frequency content? You may not need a sub.
Finally, when you hesitate between two models of speakers, then you could ask for our opinions as to which one would be a better match for the SR8012.
