Two buddies of mine have GA-X58A-UD3R's one a rev 1 and the other a rev 2. Both have Crucial C300's on the SATA3 ports and they work fine. I have seen CDM scores and they smoke anything and everything else out there. I'm unsure of the actual configs, aka bios controller mode, driver used or if TRIM is actually working as I did not set the systems up. If I had a C300 I would be using the SATA3 controller unless I proved it will not work myself.
Bill