Welcome to SPCR!
I am afraid that I can add very little about quietness of the CM VS series other than to note that the bearing of the V650S fan is supposed to be ball bearing rather than 'HDB' or sleeve bearing on the 450. However at idle I suspect the difference in noise will be minimal as the fan will be spinning about 600rpm in both.
With regards to reliability all I can say is that it has 5 year warranty.
Thanks a lot Mark, both for the welcome and help.
I didn't know that detail about the fan. I thought there to be only a difference between the VS and V series when it comes to which kind of fan is used. I guess I will see how it is with the V650S since so far it sounds good overall. I reckon if it's too noisy in any way I just make use of my 14 days return guarantee.