You really seem to want to use a Studio 20 as your CC speaker. IMO, you should buy a Studio 20 and use it as your CC speaker.
You will have three of the same speaker across the front - which is the ideal configuration - and you will be happy
Well, I haven't made up my mind as of yet. The idea was the c690 as the center with Studio 20's for the mains. As weird as it sounds, the 690 might be more acceptable from an aesthetic point-of-view given the orientation of the speaker vs the Studio 20. My cabinet will be low profile so if I go for the Studio 20 it won't be in the way of my display, but from a looks perspective, the traditional center speakers look more natural than 3 bookshelves across the front stage, at least that's what I think.
I appreciate your opinion concerning the 690. It's hard to imagine that it wouldn't be able to handle the content with ease. But then if I have a chance of going for the ideal .... LCR across the front stage, then .... dang, it's I'm just finding it hard to make up my mind. The other problem is that a 690 will look so out of place in an apartment with two small bookshelf speakers.