As excellent as the little powerpoints are(especially as rear speakers), they are not strong enough dynamically to properly handle what the center channel mix is getting!!!! You need to use the MCS1 as your center if you can! This is using two mid/bass drivers in a ported enclosure, which will handle dynamics and dialog intelligibility MUCH MORE EFFICIENTLY than what the power points can dish out! If you doubt, just call Thiel and ask them(Probably get Sheri)!
While the power points are very clean, clear, musical, and detailed, they won't carry the action you need upfront for the most demanding Center action. I say this from much experience with Thiels, and other lines.
Also, if you where interested, you might ask Thiel what they thought was a better match for Left/right speakers for your application. I bet they'll recommend the 2.3's over the 3.6's for match with your MCS1(should you go that route)
Actually, the 2.3 is a better match for your center channel choices(MCS1/scs3). But, maybe you like your 3.6's for music or whatever(I actually prefer 2.3's).
Good luck
