Does anyone know the basics of SCSI?

1: no
2: can be (usually is)
3: both

was replaced by SAS (serial attached SCSI, think of it like sata replacing IDE)

To echo mindless728... No, not unless:

1. You need a large number of drives (scalability).
2. You need dual-ported drives (redundancy).
3. You need backplane/enclosure reporting (manageability).
4. You need the fastest and most reliable drives available (performance).
5. You're willing to pay a premium for controllers.
6. You're willing to pay a premium for drives.

(1), (2) and (3) apply regardless of whether you use SAS or SATA drives. (Lots of SAS controllers/backplanes out there with SATA drives plugged into them because that's the only reasonable way to scale up the number of drives without a controller/cable nightmare.) OTOH, if (4), (5) and (6) apply, a couple SAS drives may make sense, even if you don't need (1), (2) and (3).

In short, it generally doesn't make sense for 99.9% of PC's, because they don't need it, and the cost-benefit sucks.