Yes, not only did they send you one without the disks, they sent the wrong model.
The RNDP6xxx is the Pro6 and has an Intel 2.6Ghz E5300 processor, has the business features and a 5 year warranty.
The RNDP6xxU is the Ultra6 and while it has the same hardware as the old Pro (Intel 1.8Ghz E2160 processor) as mdgm pointed out only a three year warrant and no business features.
While I realize from the extension of the models, that you are down under, in the US from Newegg, the RNDP6310 with shipping is $2,048US while the RNDP600U is $900US. Quite a difference. The diskless Pro6 (RNDP6000) is $980US. (The reason the version with disks is so expensive is they are enterprise class disks with 5 year warranties where consumer grade disk only have a 1 year warranty, but are typically around $90US.)
If you don't need the business features such as the Active Destop, and are satisfied with the 3 year warranty, the speed of the Ultra6 is more than capable of saturating a gigabit network connection when transferring files. However, if you plan on loading a number of add on's then the additional processing speed of the Pro6 may be worth it.
If it were me, I would return it to get a RNDP6000 (Pro6 diskless) and put my own disks in. Of course it depends on the price difference there, but here there is such a little difference, it would be worth it to me for the additional warranty.
Remember - the NAS is not a backup plan.
Backup = Good, No Backup = Bad