AnandTech reviews the QNAP TS-451+ NAS.
A look at the specifications reveals that the core SoC and memory capacity seem to be similar to the TS-x53 Pro launched last year. However, while the TS-x53 Pro targets the mid-end SMB market, the focus of the TS-x51 is more towards the home consumer side.
Source: QNAP TS-451+ SOHO NAS Review