Can my room support the Dynaudio C4s?

I think you are pushing it. At the very least, I'd recommend extensive room conditioning treatments. I had mine in a 15' x 21' x 7 room and found them very fatiquing until I added eight GIK 244 panels to my room. I've since moved on to speakers better suited to my room size. Also, I found the C4's to sound their best at high volume levels, which is another reason I sold them.

Make a dealer work for you. Get one to give you an in home demo.

IMHO, for your room size I think the C4s are too much. The C1s, Sonus faber Auditor Ms or Joseph Audio Pulsars would be perfect for that room size. Use a REL sub base system (G2) for the lower octaves.