I have found that most manufacturers of multichannel main/surround/center speakers VOICE the center channels to match their offerings.
The specs may be the same for the center and mains but the center channel may have a different dispersion design.
In the case of M&K (S-150) - I found their center channel speakers to be too directional. People seated anywhere but the sweet spot were missing the dialogue.
I decided to use a Sunfire CRM-3C. This has been a great addition.
No, it does not have the same VOICING as the remaining speakers but it solved my issue.