As far as I remember Legacy bios will not support BOOTING from hard drives that are over 2tb, but you should still be able to use them for storage perfectly fine. You will just have to partition and format them as GPT (GUID Partition Table) disks.
But still a uefi bios is nice, even for other things... building a new computer? might as well go with new tech. Unless you just wanna get a generally better board but with legacy bios. Either option should be perfectly fine for you.