I own a pair of CS3.6's, and I picked up an SCS3 to use as a center. I am very, very happy with this match-up. I am sure that the MCS1 would sound nice, too, but it is simply too large to use for my system. The SCS3, however, has greatly exceeded my expectations. It has a very big sound for a small speaker. Look at the specs on it. It actually goes lower than the MCS1 (or the CS1.6), although it is not as efficient. I was considering a non-Thiel center channel speaker (and was leaning towards NHT), but after A/B-ing the NHT to the SCS3, there was absolutely no comparision. I think that if you stay within the Thiel range, you should be good.
As for 2-channel versus HT, for music, I have not heard any recordings in 5.1 (DVDs and DVD-A, I don't have SACD, yet) that image as well as the 3.6's on their own. As you know, soundstage and imaging are very good with the Thiels, and at least in my system (http://cgim.audiogon.com/cgi-bin/vs_user.pl?vdone&1066244053&viewmine&publ), for music, 2-channel can't be beat. That said, I totally agree that for video, you need to have a speaker in close proximity to the screen to keep your vocals centered.
Hope this helps, Tom.
As for 2-channel versus HT, for music, I have not heard any recordings in 5.1 (DVDs and DVD-A, I don't have SACD, yet) that image as well as the 3.6's on their own. As you know, soundstage and imaging are very good with the Thiels, and at least in my system (http://cgim.audiogon.com/cgi-bin/vs_user.pl?vdone&1066244053&viewmine&publ), for music, 2-channel can't be beat. That said, I totally agree that for video, you need to have a speaker in close proximity to the screen to keep your vocals centered.
Hope this helps, Tom.