Depends on the rest of your chain, on how transparent and resolving it is. If you can hear a slight bit of harshness with your M7, then the r2r 7 will be worth it. You need a great transport for both and i2s seems to be the ultimate. A clean usb signal does also make a difference, if you go the usb route. You don't have to. Many use the Mano streamer on the french forums, seems excellent from the comments. I use a singxer f-1 combined with a wyrd and an intona, plus a couple of jitterbugs. Fed by a mac mini with internal and external ssd. Kingwa will possibly release a new usb interface at some point and i expect it to be awesome.