Choices, choices... I'm leaving choice of brand to others, and just commenting on RAID setup.
1) 2 disks, RAID 1. Simple setup, no hassles, high redundancy. If you don't need more space that that, it's not worth going for more complex setup immediatelly.
2) 4 disks, RAID 1+0. Fast, high redundancy.
3) 4 disks, RAID 5. The CPU is there to do XOR and that's it. Decent redundancy, cost-effcient space.
In case the first option is viable (you don't need more space just now), I'd go for twin SATA disks that support NCQ with the option of upgrading with many disks and NCQ-capable controller later on.
The other way would be to check what you already have in other computers and might want to replace later on, building the setup with the assumption that you're going to put your old disks to this computer later. Then the choice centers on what you already have.