I, for one, believe that pixelmixture's question is relevant and an interesting discussion.
If the hi-res files are or not really hi-res is a completely different discussion. Let's say they are, or at least will be at some point. Then, his question still stands unanswered!
I do believe that not being a 'true' analog amplifier, that re-digitizing could prove prejudicial. At least, a good computer using all its power to down sample to formats that the IDA-8 could understand may be a better resulting sound that the analog signal being digitized back by the ida. This would take the meridian out of the equation.
Another route would be to get a true analog amplifier that does not re-digitize the signal. That may prove more expensive, as it is taking the ida out of the equation, but buying new equipment.
If option A is the route, you would need to make sure that the best posible downsampling is being achieved. If you leave it to a less-than-best algorithms, then you will ciertainly be loosing a lot of the hi-res files.
Good luck, let us know which route you took! Best regards,