Or the X11SSL-F with just the HBA and 1PCIe x8 and 1 PCIe x4 for future expansion at about $250Without any 10G client ? Yes its future proof but ...
The SAS HBA onboard might be good to get the 2 slots for mirror'ed boot drive (and maybe a cache drive later)
Re drives - have you thought about pool layout already? Mirror Or Z-2/3 ?
edit : removed double quote