Will I notice any performance differences?
Mechanical HDDs are only pushing 120-150MB/sec, barely hitting SATA-1's performance ceiling. SATA-2 is not going to be a limiting factor on those any time soon.
The main benefits of SATA-3 are for either:
- high-performance SSDs
- SATA port replicator (large storage arrays)
For most people, SATA-3 is only needed for SSDs where the better ones can push over 500MB/s.