TurboNAS is the general name for QNAP NAS, no differentiation.
All Intel-based brick enclosures carry the "Pro" extension / All Rackmoint enclosures carry the "U" extension, -RP Redundant Power supplies (2) vs. -SP Single Power supply
Four bays, Dual-Core Atom - sorted from the latest to the older releases - key feture difference
TS-469 Pro Atom C2700 2.13 GHz, 1 GB DRAM (one fee slot can addd up to 2 GB), addtl. USB 3.0 ports
TS-459 Pro II Atom D525, 1.8 GHz, 1 GB DRAM (one fee slot can addd up to 2 GB), addtl. USB 3.0 ports
TS-459 Pro+ TS-459U-RP+/SP+ Atom D525, 1.8 GHz, 1 GB DRAM
TS-459 Pro TS-459U-RP/SP Atom D510, 1.66 GHz, 1 GB DRAM
These are all
The TS-459 Pro can no longer be ordered from the factory.
For details pls. consult www.qnap.com