Can my room support the Dynaudio C4s?

Great question. My first gut feeling is no but were you considering original C4's or the new MKII? I ask because the MKII sounds so much better at lower volumes when compared to the originals which might work. Like Pdreher mentioned the originals sound the best at higher listening levels. That being said I am assuming you would be placing the speakers on the short 15' wall.

I base this info on the fact I had origianl C1's and have since upgraded to the C1 Signature in Mocha. I also have a Rel B3 sub. Ideally if possible an in home demo would be way to go.

That's a huge jump coming from the SF Luitos. My room is approx 26 X 12 with the speakers on the long wall and for me the C2's were too much. What I mean it was a huge wall of sound. In the sweet spot I heard no more bass but everywhere else I did. After 6 days of listening I put my original C1's back and much preferred the sound in the sweet spot. Maybe I could get used to the sound but decided to keep the C1's. Again I demoed the originals not the MKII's and all original confidence series sounded better as you turned them way up. I highly recommend an in home demo if possible because the C4's are a huge chunk of change.