The issue of an all in one vs a well setup separate system is moot if the all in one doesn't work.
The Auralic Vega is a much more advanced dac than the board built into the Olive, J River running on a touch panel is easy to use and you can even hide the computer and control J river from an Ipad.
The sound of the Vega is very analog like you should listen to one it is amazing, and the images are very palpable.
To spend more money on a proprietary solution which costs more, and does less from a company with poor customer service is a dubious proposition, and maybe the Olive's headphone amp is quite good but I am willing to bet you can spend $500-750 and get a very nice out board one, I would say don't fight it until you've heard it, also can the Olive handle DSD, Double DSD, 32/484K tracks, and can you download directly from HD Tracks into it?
I had an Olive for a short time, no comparison, sold it, separate well setup computer beats it everytime.