Hmmm, having a quick peruse I think you've got a few options:
According to wikipedia if you want SATA 3 and RAID 10 you're looking at the A75 and A85X chipsets for APUs, or SB850/SB950 for an AM3+ platform. As far as I can see there are no Intel consumer chipsets that support more than 2 SATA 3. So if 6 SATA 3 is a must then it's AMD, and probably A75/A85X (unless you can find one of the rare 880G/SB850 motherboards with an AM3+ socket -
they do exist if you hunt
).
However, I've got to ask -
what do you think you'll need 6 SATA 3 ports for? Unless you're planning to raid a whole load of SSDs together, SATA 3 is going to be wasted on your storage array. If you want to boot off an SSD then run a large storage array on HDDs, a cheapish H77 motherboard should do the job (2x SATA 3 + 4x SATA 2) e.g.
this MSI, add a
low-power dual core Celeron,
4GB RAM for < £20, and you've spent ~ £110 on a very capable, low-power, storage server.
EDIT: as Agent says, if it'll be doing anything that a decent GPU can be used for FM2 may be a better option, but from what you said in the OP it sounds like it's just going to be a storage server?