Thoughts:
- As mentioned, the compressor could be useful to do compression while tracking before hitting your convertors.
- The Quadraverb - particularly if it's the original (there were several later iterations) - is kind of ancient. It may not be highly useful. If you use it in place of a plug-in reverb, you do reduce the amount of processing load on your computer. Whether that's of use depends on the computer and what you're doing, I suppose.
- I think the Quadraverb has a s/pdif out, so you could use it a standalone DA converter. I don't think there's anything particularly stellar about its conversion, and it's probably fixed at 16/48, so that's not all that enticing a scheme. I suppose there are (somewhat unlikely) hardware setups where it might come in handy.