The Grace SDAC Balanced just beats the DACMagic Plus on technicalities. Signature wise, the Cambridge unit is a bit smoother/warmer in its presentation (more laid back) the Grace is more incisive and dynamic. And in terms of sound, switching from one for another would be more of a side-grade than an upgrade (regardless of which direction you went in).
For more than that, you’ll have to wait for my review.
I’d wager they’re going to sell as many as they can make, regardless. But the 4490 is not a drop-in replacement for the 4452 and would have resulted in more changes … and takes a bit more work to get the best out of, so the price difference is likely to be larger than you’d think.
Per my comment above, I’ll have a proper review of it out shortly. Possibly today, depending on how my travel goes. Though I’ve not heard the Matrix Mini-I.
Most DAC chips have true differential output. You don’t need two to get balanced stereo output from the DAC IC or to do a fully balanced/differential DAC. There are rare exceptions, but this isn’t one of them.
The reasons you use more than one DAC chip are because a) in “mono” mode, many DAC chips can realize an improvement in dynamic range, noise and distortion and b) because you want even better stereo separation. It has nothing to do with being balanced.
If the output from the DAC IC all the way to the XLR connections is a +/- signal rather than a +/GND signal, then it’s true/fully-balanced/differential. There’s nothing more to it than that.
Dual-mono implementations do not mean balanced/differential, either for DACs or amplifiers.
Of course, while the DAC IC will generally have differential output capability built-in, you do need more parts than a single-ended implementation, since you will usually need to buffer that output, so you’ll need different/more op-amps or discrete parts in the buffer etc.