To the OP.., i like your plan of getting the 2 channel sound right and merging into it, the surround capabilities. I bought my front main speaker pair based on their sound while listening to 2 channel and knowing that the company also produced center and surround channel speakers. As a minimum, you want the mains and the center channel to be at a minimum from the same company and better, from the same family for timbre matching. If you want to listen to multichannel music, buy the surrounds from the manufacturer and family.
Many people disagree with my assessment of a center channel importance but it really depends on how wide the listener position is and how good a soundstage, tne mains throw. While selling a house, I had to simply the basement setup which meant that I had to store the center channel speaker for 3 months. Because the listener position angle from dead center was very narrow, I never missed the center channel at all. My fronts handle that duty as well and dialogue remained as clear and anchored as if the center channel was present. That being said, if one has a wide listener position, then a center channel is needed to anchor dialogue to the display.
