The TS-453 Pro comes directly compete with the new DS-415 + Synologie. Both have their advantages and disadvantages. Personally I chose the Qnap because in addition to providing the basis for what any NAS has to offer, it incorporates convenient features virtualization and multimedia player. So yes if you have a purely pro use multimedia has no interest but if like me you opt for such a machine for personal use then I would strongly advise you that model.
Indeed, the TS-453 Pro incorporates the HD Station function that allows you to transform your NAP player XBMC via HMDI socket on the back. It also allows you to virtualize Windows, Linux and even Android by simply connecting a keyboard and mouse to the USB ports. The quad-core Celeron processor works wonders and by upgrading the RAM to 8GB (very easily with a screwdriver) then you will have a ready server for a few years!
QTS operating system is very well done. For once I think Synologie keeps a step ahead but Qnap has made great efforts at this level and the gap is narrowing more and more in terms of ergonomics and ease of use.
A NAS upscale but with infinite possibilities!