YOu guys may be on to something, I mean it may be terrible with normal hard drives? Not sure, I've only ran SSD's on it.
And from what absic115 just said I can see why he is having issues, the Marvell driver is terrible and causes all kinds of freezes ans stalls.
You need to do a clean install, without loading ANY drivers so that MSAHCI is loaded, I know none of that is worth it for you guys, but it would be the only way you can do it now as it seems the way you setup the OS install it's going to fail when trying to switch.
I'll do some tests for you guys later today, it will be with C300 though, but you should still be able to get some idea of what gains you might get with the change. I'm not sure how big of a difference it really makes as I haven't checked on the Marvell controller, but I know it's a pretty hefty difference on the Intel controller.