Supermicro has a ton of mainboards with ECC support. Many of them have integrated "RAID" or JBOD. 8 SAS + 6 SATA is typical. I haven't checked the prices for a while, but last time I bought, it was about $250 for a mainboard with integrated 8x SAS JBOD and 6x SATA. Very cheap, when you consider no separate JBOD card is required.

Those boards and their SAS chipsets (LSI SAS2008, etc.) tend to be well supported on platforms capable of running ZFS, like Solaris, FreeBSD etc.

Other typical goodies include IPMI (integrated IP-KVM), good quality dual NICs and generally good quality components.