Both interfaces are very impressive. The Symphony Desktop and the Symphony Mk II are different in what they do, not in quality. The SE I/O modules are the best Symphony Mk II modules. The Symphony Mk II is the right choice if you're recording more than two instruments, mixing in surround or immersive, or using lots of outboard equipment with inserts for effects.

For audio, there's no need for Thunderbolt bandwidth. The Symphony Mk II comes with Thunderbolt 2 because there's no difference in performance between Thunderbolt 2, 3, and 4.

The new 16×16 SE I/O module is the first Apogee product to be equipped with the ESS 9822pro A/D chip. Like everything from ESS, this module sets new standards in A/D conversion. Another innovation of the new SE I/O module is the use of a new ultra-low distortion analog output driver capable of driving headphones. Apogee has found that the analog output stage is critical to maintaining the quality of the entire Apogee signal path.

Apogee's core competence is digital converter technology. The cascaded power supplies, the C777 clock circuitry, the analog parts of the A/D and D/A converters, and the constant current headphone output are all part of what makes the Symphony a top-quality product. The Symphony has always had a fully balanced signal path, including fully differential analog operational amplifiers. Other interfaces may offer balanced inputs and outputs, but they have an unbalanced internal signal path and often use lower power operational amplifiers. Apogee uses a 32-bit digital attenuation process, so there is no loss of resolution to worry about.

This video shows you exactly how the Symphony MKII Thunderbolt works, including monitoring and Atmos.